Ravenous Sliver

Whenever a Sliver enters the battlefield under
your control, transfuse X, where X is that Sliver's
power. (To transfuse X, exile the top X cards of
target opponent's library. Until end of turn, you may
cast any number of instant or sorcery cards exiled this
way and you may spend mana as though it were
mana of any color to cast those spells.)
Don't let your mind wander around too much. It
might stumble upon very unpleasant company.