Not only Gao, any of his spirit. Besides lauho. He haven't made a contract with Eli yet
Anyway, i dont remember anything about spirits not being allowed..the judges didn't say anything about it.
Besides, summoning spirits uses up magic. But...whatever man. I gotta idea, so yeah.
Eli is going to borrow power. I still think this isnt fair.
If god slayer magic was allowed,than im pretty sure celestial spirits are to. If i recall,that girl with the sword defeated that other celestial wizard