Arena of the Ancients does shut down legendary creatures, but the effect is symmetrical, so unless you specifically craft a deck that avoids them, it's going to impact you too
You might not care about losing coin flips with it, given the potential damage you get from spells with higher mana values
Foil-etched display commander for collectors
In Standard or Pioneer, Sephiroth could be the missing piece to an Aristocrats deck
Transforming this card into Green Goblin, or just casting it outright means youll have cost reduction on all spells you cast from your graveyard (not only instants and sorceries), and you can set up an engine where you discard a card and immediately cast it for a reduced cost
you can just play a regular game without ita necessity for a commander thats often killed on sight due to a proclivity for dropping Eldrazi titans into play