Cthulhu Wars requires a number of changes to be an effective two-player game. First, ensure that you and your opponent are familiar with the basic set of core game rules. You do not need any components or expansions beyond the base game to play Cthulhu Wars with two players.
When a Unit is Eliminated or Killed, the opposing player gains Doom equal to that Unit’s Power cost! However, when a Unit is replaced by another, no Doom is gained.
Some Units have variable Power costs. In this case, the Doom gained is equal to the average of the Unit’s different Power costs added together, whether or not the Power benefit is currently in effect. Always round up the final total.
Units which are able to avoid death by means of Abilities or Spellbooks still provide Doom to the enemy which “Killed” them, but only half as much (rounded up).
All adjustments to Actions are described below:
Before taking your turn, you must pay Power equal to the position of the Decay Marker on the Doom Track. This marker starts at 0, and then starts to increase when the other player runs out of Power, in effect penalizing you for taking multiple Actions in a row. If you can’t pay for Decay, or if you have 0 Power left after you pay, then set your Power to 0, and proceed with the next Phase.
When Unlimited Battle is unlocked for a player (by possessing 6 Spellbooks), the other player also immediately gains Unlimited Battle.
You cannot voluntarily drop to 0 Power. If you have 1 or more Power on your turn after paying for Decay, you must perform an Action.
If you are out of Power (or, for Windwalker, if you are Hibernating) when it would be your turn to take an Action, instead increase the Decay Marker by 1. Then the other player takes their turn.
Rich has 1 Power left, while Frank has 10. Rich decides to Recruit an Acolyte, going down to 0 Power. Frank then takes his turn, Moving 1 Unit. Now Frank has 9 Power. Rich is out of Power at the start of his turn, so he bumps the Decay Marker up to 1. Frank now pays 1 Power for Decay, then takes another Action (declaring Battle, for 1 Power). Frank is now down to 7 Power. Rich is still out of Power, so he bumps the Decay Marker up to 2. Now Frank, before taking his next Action, pays 2 Power for the Decay Marker. His Action is to Recruit a Cultist, for 1 Power. Now Frank is down to 4 Power. Rich, on his “turn,” moves the Decay Marker to 3. Frank pays 3 Power and then has 1 Power left for what will be his last Action of the Phase.
Some of the normal rules and Spellbooks from Cthulhu Wars need adjustment for the two-player game.
In a 2-player game, some Factions may grief Windwalker by not taking their 6th Spellbook. Therefore, only in a 2-player game, Windwalker may fulfill his "Another Faction has 6 Spellbooks” requirement by sacrificing Ithaqua, instead.
The damage from the Decay Marker is significant, and significantly changes the flow of the game. Early game strategies that work in multi-player games of Cthulhu Wars may no longer be effective in the two-player version. However, rest assured that new strategies have arisen to meet that challenge, and the game has as much depth, aggression, and chicanery as before. Have fun exploring!
Keeping your Great Old One alive is even more important than before, because his death gives the enemy a major Doom boost. Some Spellbooks become more important—Ghroth, for instance, is now one of the mightiest weapons available to Black Goat.
Also, choosing when to NOT use abilities can become a critical decision. For example, Yellow Sign may not always want to use Passion’s Power gain (since it’s not always beneficial).
Petersen Games advise against using Bokrug, Servitors of the Outer Gods, the Dhole, or the Library of Celaeno map for the two- player game. That said, it’s your game and you can do as you please.