Vengeful Spirit

Vengeful Spirit is not a creature unless it has
at least 5 corporeal counters.
Whenever an opponent destroys a creature you
control, add one corporeal counter to Vengeful
Spirit.
{1}{w/b}{w/b}, remove a corporeal counter from
Vengeful Spirit: destroy target attacking creature
an opponent controls.
Whenever Vengeful Spirit has ten or more
corporeal counters, transform Vengeful Spirit.