Chromium's Assasin

Muted (This creature can't be blocked and
can't attack planeswalkers.)
Chromium's Servant's power is equal to
the number of instants in your graveyard.
{x}, {t}: Sacrifice a creature: Create a token
copy of Chromium's Servant, except it's
an X/X. It gains haste. Exile it at the
beginning of the next end step.