Game In Session is a buff (with a debuff-like effect) placed on all players once the Chess Event in Karazhan has been initiated. The debuff applies a blanket silence and pacify effect. Once the initial Chess Event is completed and the dusty chest with loot appears, the debuff is removed.

However, if players re-initiate the Chess Event afterwards, this debuff is re-applied to all players, making any further progress in the dungeon difficult.