Ashaya's Enduring Bond (34)

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Discover X, where X is the amount of mana spent to cast this spell. (Exile cards from the top of your library until you exile a nonland card with that mana value or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.)
Ashaya's Enduring Bond can be your commander.