Infectious Ooze

At the beginning of your end step, put a decay
counter on each creature you control.
Creatures with one or more decay counters on
them are Oozes in addition to their other types.
Creatures with two or more decay counters on
them get +1/+1 and gain trample.
Creatures with three or more decay counters on
them are copies of Infectious Ooze.