Leech Wurm

Lifelink
Whenever this creature blocks or becomes
blocked by a creature, destroy that creature at
end of combat.
Whenever this creature deals damage to an
opponent or planeswalker, put +1/+1 counters
on it equal to the amount of damage it dealt to
that player/planeswalker. Then, if this creature
has 4 or more +1/+1 counters on it, you may put
a Trample counter on it.