Gav Riel, Eternal Hunger

At the beginning of each upkeep, if Gav Riel,
Eternal Hunger is untapped, create a Food token.
{2}{g/w},{t}: Exile target nonland permanent until
Gav Riel, Eternal Hunger leaves the battlefield.
Then create a Food token.
{u}, Sacrifice two Food tokens: Draw two cards.
Sacrifice three Food tokens: Untap Gav Riel,
Eternal Hunger.