Grimfel, Shadow Stalker

Deathtouch, flying

{b}{b} - Pursues (Attach Grimfell, Shadow Stalker to targeted creature opponent controls. At owner's upkeep, owner must exile cards from the top of library equal to Grimfel Shadow Stalker's toughness to save the targeted creature. If creature is saved, Grimfel Shadow Stalker remains attached to targeted creature, and owner must repeat the process on next upkeep. If opponent does not pay, target creature is destroyed, then Grimfel, Shadow Stalker ret