Durse, Thief of Essence

Whenever a Rogue you control deals combat
damage to a player, exile the top card of that
player's library. You may cast that card for as
long as it remains exiled, and you may spend
mana as though it were mana of any color to cast
that spell.
Spells you cast from exile cost {2} less to cast.
"You are under new ownership."