Illusion ability

The Illusion ability (previously called Skulking) is a slang term used to describe the triggered ability of creatures which have to be sacrificed when they become the target of a spell or ability.

Originally the effect was seen on black creatures (Skulking Fugitive, Skulking Ghost and Skulking Knight), but it is now seen on blue Illusion creatures. Some more recent designs have restricted the ability to only trigger off spells (Departed Deckhand, Labyrinth Guardian).