The Precursor

Hexproof, indestructable
When you cast the Precursor exile all permanents
you control, your hand, your graveyard and your
library.
Whenever you would draw one or more cards you
gain 3 life instead.
Whenever the Precursor attack exile target
permanent.
The Precursor has all abilities of all permanents
exiled with it and its power and toughness are
equal to the number of those cards.