Medusa

This enters the battlefield with X +1/+1
counters on it./Whenever you put 1 or more
+1/+1 counters on another colourless creature,
you may put a +1/+1 counter on Medusa.
When This dies, manifest a number of cards from
the top of your library equal to the number of counters on it.
(Put them onto the battlefield face down as 2/2 creatures. Turn them face up at any
time for their mana cost if they're a creature card.)