Seath, Betrayer of Dragonkind

Flying, Menace
When this creature enters the battlefield,
Surveil 3. Then you may cast an instant or
sorcery spell from your graveyard with converted
mana cost X or less without paying mana.
When this creature leaves the battlefield, you may
cast an instant or sorcery spell from your hand
with converted mana cost X or less without
paying mana. If you do, exile this creature instead
of sending it to the graveyard.