Edix: I have not picked up this quest yet. I have played poker with 3 people, monk, dwarf smithy, human merchant. I assume at some point you trigger something at the quest appears and you can play the two guys that wont play with you. Can anyone tell me what I have done wrong?
SPOILER WARNING!
Hey Mate, i checked out the game guide for you and it says in here that the quests is triggered by playing *winning* against some dudes sititng at a table in flotsam. (Casmir & Bendeck - weakest. Sindram - harder) once you beat Sindram he'll then let you tackle the other harder poker challengers who you can find in the craftsman quarter.
WARNING: You need to complete the free DLC Troll Trouble quest before finishing your Poker challenge quest to obtain the Troll head that the very last Poker player will offer you instead of money. Otherwise you will never be able to complete Melitele's Heart quest without having to kill the troll for his tongue.
Let me know if that helps you out.