Tai, Midnight Thief

Flying, Skulk
Whenever a creature you control deals combat
damage to a player, you may pay {1}{b}. If you do,
exile the top card of the that player's library face
down. You may look at and cast that card for as
long as it remains exiled, and you may spend
mana as though it were mana of any type to cast
that spell.
"We all wear a mask."