Traxwyrm

{1}{r}{g}{t}: Choose one: Put a non-black creature
with power 3 or greater from your hand into
play, or return a non-black creature you control
with power 3 or greater to your hand.
At the beginning of each player's upkeep
Traxwyrm deals 1 damage to that player if he or
she controls any black creatures.
Useful for moving around under the surface, so long as
you stayed clear of their mouth-full of fangs.