Player's Handbook[]
The character knows most common games of chance and skill, including cards, dice, bones, draughts, and chess. When playing a game, the character may either play out the actual game (which may take too much time for some) or make a proficiency check, with success indicating victory. If two proficient characters play each other, the one with the highest successful die roll wins. A character with gaming proficiency can also attempt to cheat, thus gaining a +1 bonus to his ability score. If the proficiency check for the game is 17 to 20, however, the character has been caught cheating (even if he won the game).
Player's Option: Skills & Powers[]
A character with this proficiency is familiar with all manner of gambling games. A successful proficiency check means the character will win a given game being played with NPCs—although cumulative negative modifiers should be assigned for each NPC with the gaming proficiency. Subtract 1 for each proficient NPC, with –2 for those with higher than basic gaming expertise.
The character might try to cheat, which confers a +3 to the gaming proficiency score and requires a check. If the proficiency check rolled is a 20, the character gets caught cheating, even if no NPCs have the gaming proficiency. Add one to this spread for each NPC with gaming proficiency—i.e., if two others have this skill, the cheater will be caught on a roll of 18–20.
Note from The Complete Paladin's Handbook[]
A paladin whose ethos includes moral objections to gambling will not engage in games of chance. Using this proficiency to cheat is a serious ethos violation.
Campaign Option: Council of Wyrms Setting[]
Gaming is described in the Player's Handbook, and covers most common games of chance and skill, including cards, dice, bones, draughts, and chess. Dragons prefer riddles, jokes, and puzzles to games of chance. If the game is not actually played, a successful check means a win. If both players are proficient, the highest successful roll wins. Cheating adds a +1 bonus to the ability score, though a roll of 17+ means the cheater is caught.
Hatchlings can't select this proficiency.