Abridged Guide to Evil Wikia

Building The Tower is a three-player game developed by Hakram.  While he came up with the initial idea during his childhood, it wasn't until he reached the War College that his friends there helped him develop it to its final form.  The game represents a metaphor for the ambitions and struggles among Praesi and other Evil factions – three players compete to achieve the goal, but they need to ally with each other to gain ground, and if no player wins within a certain number of turns, the game ends with no winner.

The final set of rules appears as follows, introducing a game between the Black Queen, the Tyrant, and the Dead King:[1]

The rules were not all that complex, and I’d had vague memories of them. Each of the three of us would begin with a hidden amount of stones: either six, eight or ten. To win one of us must gather twenty stones, and those could be obtained both by taking from opponents as well as from the ‘kingdom’, a pile of fifteen stones all could see and take from. Acquiring stones had a tad more nuance to it, for taking from an opponent required the assent of the third while taking from the kingdom could be done without. One could destroy one’s own stones, one at a time, also without assent. The game ended in common defeat should twenty full circles pass without anyone having raised their tower, as the kingdom being plundered ‘rebelled’. The last detail was the ‘pledges’, bargain struck between opponents.
Anything could be agreed on, with the only forced detail being that a number of stones had to be ‘pledged’ as collateral by both sides. Should one of them then break the pledge, the stones would be obtained by the wounded party.