Zkterdaz, Silent Stalker

Devoid (This card has no color)
Hexproof, Flash
Whenever Zkterdaz blocks or becomes blocked, it
loses Hexproof and gains Deathtouch and
First Strike until end of turn.
Whenever a creature dealt damage by Zkterdaz this turn dies, exile it. For as long as it remains
exiled, you may cast it, and you may spend mana
as though it were mana of any color to cast it.
{b/r}{b/r}{w/u}{w/u}, pay 4 life: Return Zkterdaz from your graveyard to your hand.