Bairn, Feral Fuzzchild

Legendary creatures you control get +1/+1.
{t}: Bairn becomes an Aura enchantment with
Enchant Creature. Attach it to target creature.
You may pay {1} to end this effect.
At the beginning of each combat, if Bairn is an
Aura, put a -1/-1 counter on enchanted creature,
then tap that creature; Otherwise, you gain life
equal to half the number of creatures you
control, rounded up.