Paxos, Source of Vermin

Paxos, Source of Vermin enters the battlefield
tapped.
{t}: add {b}, {r}, or {g}.
{b}{r}{g}, {t}: Regenerate target Insect, Rat,
or Wurm.
Where scavengers nest in hollowed-out rib cages
and chittering crawlers peer from empty eye sockets,
few dare to trespass.