Murders at Karlov Manor (!MKM) 

Enchantment - Case 

 

When this Case enters the battlefield, create a 2/1 black Skeleton creature token and suspect it. (It has menace and can't block.) // To solve - You control no suspected Skeletons. (If unsolved, solve at the beginning of your end step.) // Solved - 1B, Sacrifice this Case: Search your library for a card, put it into your hand, then shuffle. Activate only as a sorcery. 

Camille Alquier