Hogaak, Arisen Necropolis (MB2-136) - Mystery Booster 2

You can't spend mana to cast this spell.
Convoke, delve (Each creature you tap while casting this spell pays for or one mana of that creature's color. Each card you exile from your graveyard pays for .)
You may cast Hogaak, Arisen Necropolis from your graveyard.
Trample