With the exception of Excalipoor, whose origins are not explained, and Bashosen, which was created in Cocoon, each of his swords are said to come from another Final Fantasy game: Excalibur comes from a hidden room in Alexandria in Final Fantasy IX , Muramasa was recovered from the ruins of Zanarkand in Final Fantasy X , Masamune was fished out of Doma's poisoned river in Final Fantasy VI , and the Zantetsuken is apparently not Odin's sword in this incarnation, but a nail shed by Chaos from Dissidia Final Fantasy
It can't scale up to kill an entire table like Comet Storm, but it sure makes for a great spell to fork or to play in a Storm deck
Yuma's a much more general lands-matter commander than Hazezon, though it does incentivize you to prioritize Deserts
On the plus side, you can summon them from pretty much anywhere, so if you can get them from Deck to Graveyard quickly, you can grab them from there when youre ready