Metroid

Flying
When Metroid is blocked by a creature, Metroid
loses its Creature type and becomes an Aura with "Enchant creature" , "Enchanted creature
can't attack
or block." and "At the beginning of enchanted creature's upkeep, put a -1/-1 counter on it.
If this Aura is removed, all -1/-1 counters are as
well.