Hogaak, Arisen Necropolis
Hogaak, Arisen Necropolis
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
illus. Vincent Proce # 202/254

Oracle Text
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
But the only time you have to pay the Commander tax is if it's exiled, since you can just get it out of the graveyard instead.
903.8. A player may cast a commander they own from the command zone. A commander cast from the command zone costs an additional 2 for each previous time the player casting it has cast it from the command zone that game. This additional cost is informally known as the “commander tax.”
The way I read that is that adds to the cost, so you have to / get to convoke or delve it out. Though you'd only have to pay the tax on exile because its graveyard castable.
I can agree though that Modern Horizons gives me a hankering for another Modern Masters set.