Battle is perhaps the most complex of all events in Cthulhu Wars. It is a player-initiated Action, and is described in the Action Phase section (see here). A Battle takes place in a single Area and involves only two Factions, no matter what other Units may be present. The Faction initiating the Battle must have at least 1 Combat among its Units in the Area. Even though Battle can be an Unlimited Action (once you have earned all 6 Spellbooks), an Area may only host a single Battle on a given player’s turn.
All Units in the Area belonging to the Battling Factions must participate in the Battle.
After the Battle Action has been paid for by the player who initiated it, the Battle proceeds through the following steps:
The first step is to use (or choose not to use) any Pre-Battle Spellbooks or abilities. As with all abilities, Pre-Battle abilities are optional unless the text says otherwise. Because they are not Actions, they typically do not require Power to use. Some of these abilities may require a particular type of Unit to be present in the Battle in order to take effect, while others may merely require one of your Units to be in play (but not necessarily in the Battle itself!).
The Faction who initiated the Battle (the attacker) uses all of their Pre-Battle abilities first, and in any order desired. The Faction being attacked (the defender) then does the same.
This means that all of the attacker’s Pre-Battle abilities take effect before any of those chosen by the defender. If the attacker refrains from using a Pre-Battle ability, they cannot choose to use any of these after the defender has chosen and used their own Pre-Battle abilities.
Some Pre-Battle abilities Eliminate, Kill, or otherwise remove a Unit from the Battle. If this happens, that Unit does not participate for the remainder of the Battle, including the remainder of the Pre-Battle step. For example, if Great Cthulhu is in a Battle and his Faction is the attacker, Cthulhu may use his Devour Pre-Battle ability to Eliminate an enemy Monster or Cultist. Any Battle-related ability possessed by that Unit cannot be used, because that Unit is no longer involved in the Battle.
However, if that Eliminated Unit had already used an ability that generated an effect throughout the rest of the Battle, the effect remains. Example: Crawling Chaos can initiate a Battle and use its Flying Polyp’s Invisibility to “exempt” Great Cthulhu’s Shoggoth. Even if Cthulhu then Devoured that Flying Polyp, the Shoggoth would remain invisible and “exempted” throughout the rest of the Battle. The Flying Polyp would, of course, be Eliminated.
If all Units of one Faction are somehow removed during Pre-Battle, you do not need to go on to the next step! The Battle is over, and no further abilities can be used. For example, if Great Cthulhu initiates a Battle against Crawling Chaos and Devours Crawling Chaos’ sole Unit, the Battle would end. Crawling Chaos could not even use Seek and Destroy, as the Battle is already over.
After all Pre-Battle abilities on both sides have taken effect, it is time to calculate Combat and roll dice. Each Unit has a Combat rating (listed on its Faction or Loyalty Card), which represents how powerful that Unit is in Battle. Some have 0 Combat, and some require a simple calculation (such as Yellow Sign’s Monsters, or many Great Old Ones). Your Faction’s Combat in the Battle is equal to the sum of the Combat rating of all of your Units involved in the Battle. For example, if you are playing as Crawling Chaos and have an Acolyte and 2 Hunting Horrors in the Battle, your Combat would be 0 + 2 + 2, for a Combat total of 4.
Both sides then roll a number of dice equal to their individual Combat totals. Players can roll simultaneously, or they may take turns.
Count up the number of 6s you rolled; these are “Kill” results. Then count up the number of 4s and 5s you rolled; these are “Pain” results. Any rolls of 1, 2, or 3 are misses; they have no effect.
There are a few abilities that are written simply as Battle abilities (instead of Pre- or Post-Battle). These abilities would modify this step. For example, Opener of the Way’s Channel Power Spellbook allows him to re-roll dice that did not roll a Kill or Pain result.
Because Pre-Battle abilities may modify Combat totals, wait until all Pre-Battle abilities have taken effect to calculate the final Combat total.
After counting each side’s Battle results, players must assign their enemy’s results to their own Units.
First, assign Kill results (dice rolls of 6). Kills are always assigned first. If the number of Kills rolled exceeds the number of vulnerable Units, ignore the excess results.
When assigning Kill results, players may choose to use any available Post-Battle abilities. These abilities typically modify Battle results or how they are assigned. Post-Battle abilities can also add a third type of result: Elimination. If a Post-Battle ability adds an Elimination, it must be assigned at the same time as any Kills. As with Kills, excess Eliminations are ignored.
Post-Battle abilities are unlike Pre-Battle abilities, as Kills, Eliminations, or any other removal from Battle does not prevent that Unit from using its own Post-Battle abilities. In other words, during this step both sides may always use any or all Post-Battle abilities they have available.
There are a few Post-Battle abilities that can be used even when you are not involved in the Battle. This is the only way that a Faction not directly involved in a Battle can participate in that battle. A key example is Black Goat’s Necrophagy Spellbook.
After assigning all Kills and Eliminations, it is time to assign Pains (rolls of 4 or 5) to your Units. As with Kills and Eliminations, ignore any excess Pains rolled. In the next and final step of Battle, Kills will remove a Unit from play, and Pains will force Units to Retreat to adjacent Areas. Kills and Eliminations must always be assigned before any Pains.
Post-Battle abilities that modify Pains may be appropriate to use when assigning Pains, rather than (or in addition to) when assigning Kills. For example, Windwalker’s Eternal ability could be used at this point, rather than when assigning Kills. Also, Crawling Chaos’ Harbinger can be activated both when a Kill and a Pain are assigned. Yellow Sign’s Vengeance is used when assigning Kills, Eliminations, AND Pains.
Importantly, once a Post-Battle ability has been triggered (whether during the assigning of Kills OR the assigning of Pains) its effect takes place, regardless of whether the Unit with that ability is also or later Killed, Eliminated, etc. In other words, Post-Battle abilities may not retroactively prevent other Post-Battle abilities from having taken place, but due to already-used Post-Battle abilities, they may modify how Battle results are assigned.
Note that many Post-Battle abilities are triggered by Kills or Pains. These are specific results, meaning that if an Elimination occurs, it would not trigger one of those abilities. For example, Windwalker’s Cannibalism requires an enemy Unit to be Killed, not Eliminated (such as via Devour, Abduct, etc.). Sleeper’s Demand Sacrifice does not protect against Eliminations, only actual Kills, etc.
After Battle results have been assigned, they need to be applied. Kills and Eliminations remove Units from the Map, returning them to their Factions’ Pools. As with assigning results, Kills and Eliminations must be applied before Pains. Both sides remove their Eliminated Units, and then their Killed units, all at the same time.
After applying Kills and Eliminations, it is time to apply Pains. Pained Units Retreat and are moved to Areas adjacent to the Battle Area. As with assigning Kill results, you choose the Areas to which they retreat. They do not need to all go to the same Area; they can be split up among multiple Areas. Note that a Pained Unit’s Retreat does not count as a Move Action.
The player who initiated the Battle (the attacker) applies all of their Pains first, followed by the defender.
You cannot retreat Pained Units to any Area that contains Units belonging to the Faction you just Battled. If this prevents your Pained Units from Retreating, select a single Unit among them and Eliminate it. Your other Units remain in the Battle Area as if they were not Pained.
If you are the attacker in a Battle and receive several Pains, a good tactic may be to Pain those Units to all the Areas around the Battle Area to completely surround your enemy and force an extra Elimination!
Some Post-Battle abilities may take effect during the application of Battle results. Many Post-Battle abilities affect the ways in which results are assigned. A key example is Crawling Chaos’ Madness (which also has the feature of being usable even when Crawling Chaos is not involved in the Battle!). Madness allows Crawling Chaos, rather than the Faction owner, to choose the Area(s) where Pained Units go.