The Reality Stone

Indestructible, equip {2}
Equipped creature gains changeling, gets +X/+X
where X is the greatest number of creatures in
play that share a creature type, and has
{3}, {t}: target permanent becomes an artifact,
creature, or enchantment in addition to its other
types, until end of turn.
Whenever equipped creature deals damage to a creature, put a changeling counter on it.
At EOT, exile equipped creature if non-legendary.