Tarniss is the grim fantasy world explored in the Dungeoneer line of card games currently available through Atlas Games. It is described in the flavor text on the cards and in the Dungeoneer Guide.

It is a peaceful world interrupted by dark forces that menace the land.

The sun has darkened, strange beasts stalk the lands. Intrepid heroes like you delve into deadly dungeons to fight monsters, gain levels, and complete daring quests while a malevolent Dungeonlord attempts to thwart you and litter the dungeon with your corpse.