Seath the Scaleless

Cascade, cascade, cascade
Whenever you cast an instant or sorcery spell, if
it's the first time this ability has resolved, Seath
the Scaleless gains flying until end of turn. If it's
the second, gain lifelink. If it's the third, draw
three cards.
And Seath the Scaleless betrayed his own, and the
Dragons were no more.