Acquisitive Mindmage

Whenever a creature you control blocks, exile the
top card of the library of the controller of the
blocked creature face-down. For as long as that
card remains exiled, you may look at it, cast it,
and spend mana as though it were mana of any
type to cast it.
Stalk {4}{u}
"I'll get your secrets if it's the last thing I do."