If you go wide or the game stalls, this could be one hell of a cheap combat trick
While its cost is only reduced by two mana and it doesn't exile, it's an instant, its base cost is five, and for the full cost it can target any permanent
Absolute Virtue Aettir and Priwen Clive, Ifrit's Dominant Cloud, Midgar Mercenary Cloud, Planet's Champion Emet-Selch, Unsundered Esper Terra Gogo, Master of Mimicry Hades, Sorcerer of Eld Ifrit, Warden of Inferno Kefka, Court Mage Kefka, Ruler of Ruin Lightning, Army of One Sephiroth, Fabled SOLDIER Sephiroth, One-Winged Angel Sephiroth, Planet's Heir Terra, Magical Adept Vivi Ornitier Y'shtola Rhul Yuna, Hope of Spira
Zell also interacts well with lands that have abilities that activate when they enter the battlefield
Through the Ages will very likely, and at long last, bring partner pairings into the Arena format thanks to Bruse Tarl, Boorish Herder, reimagined as Final Fantasy XVI's Hugo Kupka (who is not really one of the good guys, as you may guess from the card art), and Tymna the Weaver as Cecil Harvey, illustrated by the legendary Yoshitaka Amano