Osis, Eternal Desperado

Indestructible
This creature cannot attack or block.
As long as Osis is enchanting a creature, it
becomes an aura.
{0}: Enchant target creature you control.
{0}: Remove this from target creature you control.
When this is removed from a creature, sacrifice
that creature and gain an experience counter.
Enchanted creature gets +1/+1 for each
experience counter you have.