Warhammer Underworlds is advertised by Games Workshop as the ultimate competitive miniature game. But what it is exactly and how complex is to start playing?
This is an Underworlds Beginner’s guide, meant to get you up to speed on everything you need to know as a beginner getting into the game. If you are new to Warhammer Underworlds, this complete list of all Warhammer Underwords Warbands might be helpful as well.
Introduction to Warhammer Underworlds Beginner’s Guide
Warhammer Underworlds (WU in short) is a competitive miniature board game with a strong emphasis on deck-building, set in the same world as Age of Sigmar, Games Workshop’s high fantasy world.
A game of Warhammer Underworld lasts 30 to 45 minutes on average and requires very little space to be played.
To play you need to have a hex-based board, a warband made of 3-9 miniatures on average, 6-sided dice but with their own symbols, a deck of cards and an opponent.
The goal of the game is to collect glory points: tokens that can be gained in different ways, from controlling objectives to killing enemy fighters. Each warband has its own playstyle: Some are better at killing, some at controlling the board but, in general, by choosing which cards to put in your deck, you decide how to score points and win the game.
Getting started with the game is actually really easy, especially the newest warband and the core sets come with pre-made decks that allow you to start playing immediately to understand the basics of the game. But to master the game… well that’s a different topic.
The last section of this guide is dedicated to other online resources you can consult to improve your knowledge of the game, from mastering your decks to keeping up to date with the latest meta, etc.
This guide is a higher-level presentation of the game to answer your most burning questions and give you an idea if Warhammer: Underworlds is a game for you.
Rule Summary of Warhammer Underworlds
Down below you can find a more detailed run-down of the rules of the game but here is a quick rules summary of how Underworlds play:
- First thing you need to decide is which warband to use from a vast list of various warbands. Each one comes with a specific, fixed amount of fighters/miniatures.
- Each warband comes with some specific faction cards that only they can use, however these decks can be integrated with universal cards available from the same or other sets
- A deck is composed of 12 or more objective cards, that allow you to score glory points once you meet the requirements, and 20 or more gambit cards that allow you to do all sort of shenanigans or upgrade your fighters
- At the start of the game you place boards, tokens and miniatures and then you go through 3 rounds in which you and your opponent alternate to perform actions
- Each round is composed of four activations per player, with different actions available involving usually moving your fighters or attacking, and a “power phase” that allows you to play extra cards. Note that you can also play cards in your opponent’s power phase
- At the end of each round you score glory points and draw new cards. At the end of the last round the winner will be the one with the highest count of glory points
So the game is pretty quick to play and the depth of strategy lies in creating the deck (before the game) and how you move and take advantage of the cards that you are dealt.
When you buy a warband you get all the fighters in the warband and a deck of cards. In that deck some of the cards can only be used in that warband, but some of the cards are universal and can be used by other warbands. So while buying the warband will give you what you need to play with that warband, you will need to buy other warbands if you want to tweak your deck to be super optimized.
Different ways of playing Warhammer Underworlds
As with many Games Workshop’s games, there are different ways to play Warhammer Underworlds. From 2-players “friendly” games, to organized tournaments, up to multiplayer games.
The game itself is shaped in seasons, with 8-10 new warbands released every season (roughly from September to June) and brand-new cards and mechanics that improve the game and modify which strategies to use.
At the time of writing (October 2021) there are five seasons currently for Warhammer Underworlds:
Warbands from any season can be used in any game, however depending on the type of tournament/match only certain cards from certain sets can be used.
These are the various ways of playing in Underworlds:
- Relic: this is the most permissive of the game formats where every warband, card or board is allowed to be used. With some restrictions: some cards are so powerful that they have been utterly Forsaken, i.e. they cannot be used at all. A complete list of forbidden cards and many more rectifications or clarifications are available in April 2022 FAQs.
- Championship: this is the most widespread format where only certain cards and boards are allowed to be played. This includes all cards and boards published in the last 2 editions or reprinted in the last 2 editions. At the time of writing (April 2022) the current legal seasons are: Harrowdeep (including Nethermaze) and Direchasm (including Direchasm – Arena Mortis and Essential Cards Pack).
- Rivals: this is the most beginner friendly set as only pre-defined decks are allowed. You can use any of the newest warbands (starting from Harrowdeep), any of the previous warbands that have at least 12 faction objective cards and 20 faction power cards, or, as in the case of older warbands that do not meet that condition, the universal Rivals deck (Silent Menace and Illusory Might the first ones published).
- Arena Mortis: a multi-player game where you use one single miniature in an arena against all other participants. Deckbuilding is part of the game but there are more twists to it.
Attention, the Vanguard system has been replaced by the Rivals system.
Each game system has its own set of allowed cards but also of Forsaken cards (completely banned) and Restricted cards (maximum 3 are allowed in each deck).
All warbands are available in each format and all cards specific to that warband are also valid independently from the season they are associated with (except in Rivals if that warband does not reach the minimum required target). This makes warbands with strong faction-cards much more durable in the advanced seasons where new mechanics are introduced.
There are other ways to play the game, for example in White Dwarf December 2018 a multiplayer game was published where all warbands have to bring down a Gargant, and in November 2019 Apex Predator plays on the concept of killing a particular fighter upgraded with a specific card (Ur-Predator), reminiscent of what will become Primacy in Direchasm.
Finally, all warbands have rules to be used in Age of Sigmar properly, although most are not synergistic or particularly useful. Despite this, these warbands can represent an excellent starting point to test your colour scheme or for alternative sculpts for existing models – in certain cases of much superior quality than the existing ones or even cheaper.
Lore of Warhammer Underworlds
Shadespire was once a prosperous city in Shyish, the Realm of Death, ruled by a caste of wizards called Katophranes. They were the first to discover how to use shadeglass, a magic substance available in Shyish, to capture the deceased souls.
This way they were able to trick death, conserving their memories and knowledge in artifacts made of shadeglass, and rule the city for eternity.
Nagash, the Supreme God of Death and the one who claims ownership of all souls, saw this as a personal insult and created a powerful curse that would punish for eternity those who dared to defy him.
This way he moved the entire city suspended between Hysh, the Realm of Light, and Ulgu, the Realm of Shadow and cursed the city to be forever tormented, with no escape and no possibility of relief in death, as every day you would be resurrected.
With the passing of years, madness filled the entire city that is now split in different shards, with wonderful artifacts forever lost to the other races and the current population just a shadow of their former glory.
Not even Shadespire could escape the consequences of Nagash’s ritual that sent Shyish energy all around the Mortal Realms.
The event, called the Necroquake, despite being corrupted by Chaos at the last moment, forever changed the laws of magic having catastrophic effects on Shadespire, the Mirrored City.
A portion of the city collapsed, and ethereal beings started to prowl the streets, souls so tortured that they now seek only to impart the same suffering on the living.
When Sigmar sent representatives of the Sacrosanct Chamber, the Stormcast chamber more attuned with magic, to unbind the enchantments surrounding the city, Nagash saw this as a personal attack on his territory.
He then opened the Nightvault, a special prison the Katophranes used to imprison all those who opposed their rule. This was no common jail as the evil souls here were tortured for eternity and now gladly accepted the found freedom even if at Nagash’s conditions.
Beastgrave is the name given to a mountain of incredible size in Ghur, the Realm of Beasts. What exactly that mountain is, is not clear. Some claim it’s a godbeast, a being of unimaginable power, some that an evil spirit lurks in the mountain. But whatever the explanation is, one thing is certain: the mountain reaches adventurers in their dreams and taunts them with whatever is their inner desire and the ability to find it in the mountain’s chambers.
It is this way that Beastgrave lures flocks of would-be adventurers to lurk in its bowels, facing uncountable dangers and other rival warbands seeking treasures that they will never find and with no possibility to escape. The longer they stay in the mountain the more primal they become. To prowl in Beastgrave is to be hunter or to be prey.
In the mountain itself there’s a trace of a long-forgotten race, the Silent People, of insectoid shape. Of them is left only a few drawings on the walls or statues deep inside the mountain. Who they were is not known, neither why they occupied the mountain, but in recent times strange sounds and movements can be seen in the darkest corners.
All of this changed when the Necroquake sent necromantic energies all around the Mortal Realms affecting also Beastgrave. Somehow the Katophrane Curse reached the mountain and now the prisoners are forever trapped in an eternal cycle of death and resurrection denying the mountain the souls it claims.
The Arena Mortis appears in arcane places increasing the lust for blood of all combatants trapped in it, raising them as soon as they die in a perpetual cycle. Nagash challenged his Mortarchs to harness the energies emanating from the Arena Mortis but all failed and their artefacts, called mortis lenses, are now trapped in the Arena Mortis appearing at random and bestowing boons to the fighter that first claims them.
Ghur, the Realm of Beasts, lives through cyclic uprisings where the entire life of the realm, from the warriors to the landscape itself, awake in a primal instinct to hunt or be hunted. It was in one of these occasions that the Ossiarch Bonereapers sent by Nagash to conquer Ghur were utterly defeated by the Destruction forces.
For Beastgrave this was a period of renewal: entice new warriors in its tunnels and feast on their torment and primal emotions. But this time was different as the Katophrane curse starved the mountain of the souls needed for its nourishment and now it was hungry! It awoke too early and its rage sent the entire mountain in disarray, with the amber previously protecting the deepest and most remote areas, the Direchasm, now liquefying and leaving exposed treasures but also dangerous beasts previously trapped.
The Silent People are much more than a rumour. They slumber in the bowels of Beastgrave between each cycle renewing their insectile form. But this time the release from the amber awoke them too early leaving them exposed in a larval stage of hibernation and forcing them to retreat deeper in the mountain abandoning all their treasures to the pleasure of the adventurers.
The setting moves to Ulgu, the realm of Shadows, in particular in the Helleflux region, deep beneath the sea. Not much is known of Harrowdeep, who built it or why, but there’s a clear connection with the Orb Duplicita, the most infamous of Ulgu’s moons. When the moon shines, it is possible to reach (or be trapped) in Harrowdeep from any water source lit by the moon, even outside of Ulgu. Shadow magic is really strong in this labyrinth and it is rumoured that great artefacts imbued with shadow magic are present at its core.
But no one ever returned from Harrowdeep. Even a conclave of Idoneth that moved over the structure together with some rebel Daughters of Khaine opposing Morathi rise to godhood, mysteriously disappeared while investigating the place. Recently disappearances, a common sight in Ulgu, have increased in frequency and Sigmar sent his spies to investigate the issue. Morathi’s spies as well discovered Harrowdeep while chasing the rebels.
At the very nadir of Harrowdeep there is the Nethermaze, an ever worse place full of all types of dangers.
How the Season Rules work for Warhammer Underworlds
You can see a detailed video on how to play the game published by Warhammer Community on their main YouTube channel. It’s related to Season 3, but most things are still accurate.
If you want to see the core rules instead, they are available for free on the dedicated website.
If you are new to Underworlds you should know this: get the latest starter set and start with that. You do not have to worry about all of the changes through the season and you will get the most up to date rulebook available at the moment.
Shadespire: Underworlds Season 1
Shadespire is also the first season of Warhammer Underworlds that set the basic rules. Those did not change massively with the passing of time, but new mechanics have been introduced each new season.
The game is divided in several phases, the first one of which is the Set Up.
This includes placing the boards, the tokens, draw the cards and place the fighters.
The boards represent where your fighters will play and there’s a strategy on which one to choose and how to place them depending on your warband and type of play.
The dice used are six-faced dice but with specific symbols representing attack and defence. Each dice will have one critical (an exclamation mark within a multi-points star), one support (two semi-circles around a dot), one half-support (one semi-circle around a dot) and two other symbols depending if it’s an attack or defence die. Each player will roll the relevant dice when instructed and the results are compared to see who wins the action.
The game has different objective tokens, 5 for a 2-player game but more in multiplayer games. These are placed by the players alternating placing tokens face-down on the battlefield and then flip them to see which number they represent. Certain cards will instruct you to hold any objective, while others will specify a determined number. To hold an objective, you need to have one of your fighters occupying the same hex at the end of a round.
The deck is composed of two types of cards:
- Objective cards representing the different ways to obtain glory points. You have to have 12 cards of this type in your deck and always three in your hand (unless you ran out of cards).
- Power cards representing upgrade cards (equipment that you can place on one of your fighters at the cost of glory points) and ploy cards that are played in the power step phase or as a reaction. You must have at least 20 of these cards in your deck, with no more ploys than upgrades and you cannot have more than 5 in your hand.
Once you placed the boards, objective tokens, drew cards and placed your fighters, you are ready to start.
The main game is divided in three rounds each alternating an action phase with an end phase. At the end of the third round you count how many glory points each player scored and the winner is the one with the highest count.
Each action phase is made of four activations per player. Any fighter is eligible to be picked, but certain actions will prevent further activations in the same round. Example of actions a fighter can take are:
- Move: each fighter can only move once per round but can perform other actions in later activations except Charge.
- Attack: attack actions can be performed multiple times by the same fighter as long as he/she is in range of their target. Each fighter has his own weapon profile with a range characteristic, how many dice to roll, which values represent a success and the damage to allocate in case of success.
- Charge: this represents a move and an attack action in the same activation. At the end, unless otherwise stated, this fighter cannot be activated again in the same round.
There are other actions a fighter can take, like discarding cards and drawing some new, but these are the main ones.
Finally, combat can seem a bit counterintuitive at the beginning, but it’s easy to understand after playing a couple of matches. Both attacking and defending player roll as many dice as indicated by their corresponding characteristic.
- If the attacker has more critical successes than the defender, the attack succeeds. If the defender has more critical successes, then the attack fails. If they have the same number, then calculate the successes.
- If the attacker has more successes than the defender, the attack succeeds. If the defender has more, the attack fails. If they have an even number, but the attacker has at least one success, the attack fails but the target fighter can be pushed one hex.
- Attacker and defender can get support from nearby friendly fighters. The Attacker counts how many he has adjacent to the target; the target counts how many he has adjacent to the attacker. Whoever has the highest number counts half-support rolls as successes. If there are more than two supporting fighters than the opponent, then count support rolls as well.
Once an attack is successful you inflict the damage linked to that attack action and can push the fighter back.
At the end of the activation, players alternate in the power step where they can play Ploy cards or equip Upgrade cards on their fighters as long as they have enough glory points to spend. Note that spent glory points still count for victory points but cannot be reused to equip other cards.
In the end phase, players alternate to score as many objective cards as they accomplished, discard any unwanted and draw new cards to have 3 Objective cards and 5 Power cards. Note that there is no drawing at the end of the third round.
In matched play you usually play the best of three games (the first player to win two games).
There are more rules and subtleties but those were the key rules in Shadespire.
Nightvault: Underworlds Season 2
The biggest change from the previous season was the introduction of magic. Certain fighters have a wizard level on their card representing how many dice they roll each time they try to execute a spell. Only wizards can attempt to cast spells.
- Ploys are now only a portion of the gambits divided in spells or ploys. The limit of no more than half of the power deck made of gambits still stands.
- Spells are not only available on gambits: they can also be used as reactions or as part of upgrades and they can be available as magic attacks for those with magic powers.
- Magic attacks work exactly like normal attacks, but instead of rolling the attack dice, you roll the magic dice.
- The rules for support, half support and critical are the same for either attack or defence.
- Another ability introduced was “innate” that allows to have a permanent modifier to a roll. For example granting at least one success to certain actions requiring that innate ability.
- Scatter ability also made its appearance, introducing random movements or effects.
Beastgrave: Underworlds Season 3
Beastgrave is the third season of Warhammer Underworlds and was a big changer. First it introduced nice reference sheets that greatly simplified how to read the Combat Sequence:
The sequence itself didn’t change but introduced a specific moment in time for every reaction.
An important change is related to the feature tokens. They now have 2 faces: one is a lethal hex and one the objective token with the number. There are now mechanics that flips these tokens denying objectives to your enemies. Normal lethal hexes still exist and can be placed after the objective tokens.
Here is a list of other changes introduced in Beastgrave:
- Now who wins the roll-off to place the boards can decide which player places his first instead of always going second.
- Guard action now prevents being driven back on top of using the Shield symbol as a success.
- Superactions have been introduced, where two or more actions are combined in one single action, for example Charge or Scything.
- Several warbands have access to different counters to keep track of a specific warband-related mechanic.
- Keywords are now clearer in the card style and many game effects play with those keywords. For example, Hunter and Quarry have been introduced giving a context to the use of some cards with Hunter focusing on aggressive cards and Quarry focussing on defensive cards.
- Ensnare and Scything have been introduced as new attack action keywords. Ensnare prevents the use of Dodge symbols in defence while Scything allows to attack multiple enemies adjacent.
- Objective cards are now keyworded too:
- Surge cards allow to score glory points immediately
- Hybrid cards have two conditions and you need to meet only one to score the glory points
- Dual cards have two conditions and you have to meet both conditions to score the glory points
Direchasm: Underworlds Season 4
Direchasm is the fourth season of Warhammer Underworlds. Not many mechanics have been introduced.
Here are some of the key changes in Direchasm:
- When creating a deck no more than 6 Surge cards can be used.
- When taking out of action an enemy with 6 or more wounds, you now score 2 glory points instead of 1.
- Supporting now does not cancel each other out: attacker counts his allies for support and defenders his own and then each one can use the support or half support dice depending on how many surrounding fighters they have.
Two new mechanics have been introduced. The first being Primacy.
Any warband can play Primacy but they need to declare it at the beginning of the game when revealing their warband and they need to have at least one card in their deck using the primacy token. After the declaration, warbands using Primacy cards can contend the Primacy token. It is possible the opponent is not able to play this mini-game giving uncontested control of the token to the other warband.
There are different ways to obtain the Primacy token:
- Some are detailed in the cards themselves
- If an unwounded opponent is taken out of action in one hit
- If an enemy leader is taken out of action
- If 4 or more objectives are held
On top of the benefits provided by the cards mentioning Primacy, at the end of each round the player holding the primacy token scores a spent glory points and discards the token.
Another mechanic introduced is Hunger that makes use of the hunger counters. Certain cards allow to collect these tokens and other cards will give you benefit or glory points depending on how many counters you have. It’s similar to other warband-specific counters but more universal.
Arena Mortis is a multiplayer variant for 3 to 6 players introduced in Beastgrave (season 3) and published also in Direchasm (season 4).
The game is quick and fun: every player has only 1 fighter and no objective deck. Instead you build a gambit deck and an upgrade deck (at least 10 cards each, no max limit) and you play on a single board.
The gambits are used in the power steps before or after your fighter’s action or as a reaction. The upgrades instead are given to a fighter at the beginning of the game depending on their Wounds characteristic and every subsequent round.
If your fighter is taken out of action it’s not game over: next round you resurrect it and play as normal after adding a Raise counter.
In addition to scoring glory points with upgrades, gambits or taking down enemies, each game one special token is chosen randomly and put at the centre of the board. Holding this objective can provide extra glory points and bonuses like more upgrades or more dice when attacking.
Building a deck for Arena Mortis is a much different experience than building it for Warhammer Underworlds but is definitely a quick paced game ideal in particular if you have an odd number of players.
The expansion set comes with a double-faced board, various tokens and counters, and a new set of cards usable also in Warhammer Underworlds games. The Sepulchral Guard also got some upgraded mechanics based on raising new fighters.
On Warhammer Community two new fighter cards are available specifically for Arena Mortis presenting a Knight of Shrouds from Nighthaunt and a Knight-Incantor of the Stormcast Eternals.
Harrowdeep: Underworlds Season 5
Harrowdeep introduced few changes to the game, shaking a bit the ductility of certain warbands favouring control warbands against objective holders.
The first thing introduced is certain new traits (Beast and Fly) that specifies which characters can control objectives and which can go through obstacles and other miniatures. Those rules were already present in the fighter cards, they are now just keyworded for all new fighters moving forward. Also each warband has now been associated to a Grand Alliance and have now access to Grand Alliance faction cards. For more information about changes on existing cards, and which GA faction a warband belongs to, we recommend looking at the most recent FAQ.
Feature tokens now have Gloom hex on the opposite side where before there was a lethal hex. A Gloom hex provides cover (full support results count as success). Feature tokens are placed on the board with the gloom side face up, therefore you will not know the objective numbers of the hexes placed by your opponent until you flip them. There are different ways to flip a feature token, one of which is to “Delve”, an action that you can perform in the Power phase instead of playing a power card.
The ability to draw new cards at the beginning of the turn (do-over) has now been simplified allowing to put back the discarded card in the deck. This means that fishing for the right card at the right time is now easier as there’s no consequences of discarding cards. The objective deck can now contain more than 12 cards as well.
Steps and reactions have now been clarified with beautiful charts.
New damage keywords have been introduced, mostly to the benefit of some future cards: Bounties are glory points obtained when killing a unit and a unit on his last wound is now called Vulnerable.
In the Power Step is the opponent that goes first in playing a card now.
Stagger has been introduced as the opposite of Guard, so that one condition is applied, the other is removed. You can now re-roll one dice on attack actions against Staggered opponents.
Buying Warbands and Accessories for Underworlds
This is probably the most difficult part to discuss. Almost all warbands for Warhammer Underworlds have been specifically created for the game and are available depending on the seasonality. The last 2 seasons are always available in all stores complete with cards.
The one exception is the previous season starter set that is usually retired when the new one is published and the two warbands within are sold separately with their cards but without all counters, dice, boards, etc.
However, since rotation makes most universal cards irrelevant, all warbands from the retired season are repackaged and sold, at a cheaper price, without cards. If you want to use a warband from the first seasons, second-hand market is your only solution, at least for the faction cards that remain valid. Maybe one day Games Workshop will reprint expanded faction cards for previous seasons, the Sepulchral Guard from season 1 got a small boost in season 3 with Arena Mortis, but so far there has been no indication.
If you are starting the game the latest starter set is definitely the best place to begin as it provides 2 warbands, 2 boards, all cards, dice and tokens that you need to learn the game with a friend and start playing.
When a new warband is released it usually comes with card sleeves and faction-specific dice that are absolutely optional but run out of stock extremely fast. However, keep an eye on other expansions like the Beastgrave Gift Pack or Arena Mortis as they often contain cards that can be really useful to your warband.
Once you have chosen a warband you will find some basic cards in the box itself to play it straight away. But if you want to win some competitive matches, being just your local game store or a Grand Clash, you will need cards from other sets. The best cards are sold on second-hand market, however, often is easier to buy an existing warband and you get some sweet miniatures in the process.
Pros and Cons of Warhammer Underworlds
Warhammer Underworlds is a miniature game at its core. It simplifies the movement part removing the need of measuring tape, counting inches and arguing if you are in range or not based on the size of your base, by introducing a hex board where you just need to count the hexes.
It is not a card trading game like other famous brands in the sense that, while you still need cards to play the game and some are extremely coveted, you will always know in which expansion that card can be found instead of relying on luck. If you need to know where cards can be found, in the resources section we link to a repository that explains exactly where to find what you need.
The miniatures are in plastic of a good quality considering the relatively low (for Games Workshop standards) price. They are, however, push fit, meaning that they are perfect for beginners not requiring any glue, and a bit less for experienced players as it requires extra work to get to the perfect stage where no line is visible. They come in different colours, so placing two unpainted warbands on the board still makes them easier to distinguish one from the other.
Strategy is important. For this reason the deck building phase will make the difference in more competitive games. The use of dice will however introduce a bit of randomness that helps to balance a bit.
This game is perfect for beginners starting a new game and for veterans to challenge each other in the more competitive scene. Most warbands are quite balanced but obviously there are few winners and few losers.
If you are a beginner don’t rush in the competitive scene or you will struggle to obtain any result.
What of using Warhammer Underworlds units in Age of Sigmar?
So you are an Age of Sigmar fan, maybe you have an army or two, why would you be interested in this game?
Well the game is fun and quick, allowing for coffee table games in your lunch break or between hours-long events at your local gaming group.
If the game, and the deck building in particular, is not for you, there are still few reasons you may be interested in following the game:
- All miniatures have rules available for Age of Sigmar. While most of those are forgettable, there is here and there a rare gem like Grashrak’s Despoilers.
- Even if the rules are terrible, you can still use these models as proxies, and in some cases they are better and cheaper models than the originals available, for example the Hag Queen or the Icebrow Hunter. Be careful to the base size, however.
- If you are unsure about starting a new army and you need some testing models, these are perfect and cheaper than buying a box of your future army.
- The lore of the game is intrinsic to Age of Sigmar lore, sometimes in parallel, sometimes forewarning of what is to come. The Kurnothi for example seem ready to take the scene in a not so distant future, while Direchasm starter set introduced us to the new wave of Lumineth and Slaaneshi models. Not all are hints on potential expansions however of which the Darkoath warband is a testament.
Extra resources for Warhammer Underworlds
Games Workshop has their website dedicated to the game where you can find more information and keep up to date with the latest news. They even have a video tutorial on how to play the game. In their Warhammer community website you can find also new free content, like two new fighters’ cards available for Arena Mortis.
If you want to hear from the horse’s mouth, who better than a Grand Clash winner? John from Can You Roll a Crit? has a blog dedicated to all Warhammer Underworlds useful information, in particular how to do deck building.
Another extremely important blog full of resources, decks and content from various creators is Well of Power.
If you want to find to which set a specific card belongs or what the exact text is, then there are different repositories online, I personally use Underworlds DB as it immediately details in which formats a specific card can be used.
Finally, it is worth mentioning that this game can also be played entirely digitally with Warhammer Underworlds: Online, available in Steam. It is a faithful adaptation of the board game introducing stunning visuals to your games complementing the board game when you have no time to find physical opponents in the real world. Most recent critical reviews are based on their sale model where only 2 warbands are available in the core game and all others are paid DLCs. At the moment of writing (March 2021) it supports only season 1 warbands and the first 2 of Nightvault set, but it’s in constant expansion so keep it monitored if you are interested.