Appa, Steadfast Guardian
{2}{W}{W}Legendary Creature — Bison Ally
Flash Flying When Appa enters, airbend any number of other target nonland permanents you control. (Exile them. While each one is exiled, its owner may cast it for {2} rather than its mana cost.) Whenever you cast a spell from exile, create a 1/1 white Ally creature token.