Cog

Cogs are pickup that is required for progression in a nightmare, cogs are usually found floating in the air but many are concealed in chests.

Each nightmare separates areas with doors marked with 10, 20, 30 and 40 cogs respectively, while 40 cogs is the minimum required to complete a nightmare some nightmares have slightly more than 40 though it is unclear if this was intended by the developers or an oversight.