Dragon Slayer

Enchant creature card in a graveyard

When Dragon Slayer enters the battlefield, if it's on
the battlefield, it loses "enchant creature card in a graveyard" and gains "enchant creature put onto the battlefield with Dragon Slayer." Return enchanted creature card to the battlefield under your control
and attach Dragon Slayer to it. When Dragon
Slayer leaves the battlefield, that creature's controller sacrifices it.
Enchanted creature gets -1/-0.