Kassadin, the Riftwalker

Flash, Ward {2}
Whenever a player casts an instant or sorcery
spell, put a void counter on Kassadin, the
Riftwalker.
Remove seven counters from Kassadin, the Riftwalker: Choose one—
• Counter target spell.
• Exile Kassadin, the Riftwalker, then return it to
the battlefield under its owner's control with
seven +1/+1 counters.