Phyrexian ArenaPhyrexian Arena is fine, but why settle for it when there are more consistent options
Just remember: theres no such thing as a perfect card in a vacuum, and despite the strength of the best enchantments MTG has, always remember to play test
Outside of that, the usual Ruby and Sapphire tendencies are there in the deck, like building up your inkwell or dealing damage and rushing down characters
Collecting Field Notes Calamity Beasts are causing havoc all around Bloomburrow, and the animals of Valley are taking field notes to stay informed on these monstrous elementals
The flexibility and potential to work as a mana or card advantage engine make it a truly powerful storm commander, even more than if it had the keyword itself
Those are your only two kill conditions