You can't spend mana to cast this spell.
Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for or one mana of that creature's color.), delve (Each card you exile from your graveyard while casting this spell pays for .)
You may cast Hogaak, Arisen Necropolis from your graveyard.
Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
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