Poppy is a resource used to restore Garrett's focus in Thief. Chewing the petals of the flower has the effect of replenishing Garrett's Focus. It costs 35 gold to purchase.

Poppies are a source of opium used for laudanum, poppy-milk and other opium byproducts.

The white species appears to be a strange mutant variety empowered with Primal and has fungus like properties, capable of growing anywhere, even underground, and glowing with inner light. Where many poppies have sprouted one can almost always find strange fungus-like vines, roots or other growths extending up the walls. Seed pods can be found in many locations where Primal is near, and often there is a haze of glowing pollen like dust in the air.