Ma'Sa the First

Changeling
Hexproof, Flying, Vigilance, Trample
Whenever a creature you control attacks, until end of turn it becomes non-legendary and gains Myriad. (Whenever it attacks, for each opponent other than defending player, you may create a token that's a copy of that creature that's tapped and attack-
ing that player or a planeswalker they control. Exile the tokens at end of combat.)