In other places, Sphere is much better
And it also divides opposing resources some - In my experience, dealing with a "go-wide" and a "go-tall" strategy is a lot harder, and Kellan allows you to play both in one concise package
First off all, it exiles, preventing your opponent benefitting from pesky death triggers
The additional booster pack should help you stay in the race with your friends
Absolute Virtue Aettir and Priwen Ancient Adamantoise Buster Sword Clive, Ifrit's Dominant Cloud, Midgar Mercenary Cloud, Planet's Champion Dark Confidant 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 Nibelheim Aflame Sephiroth, Fabled SOLDIER Sephiroth, One-Winged Angel Sephiroth, Planet's Heir Summon: Bahamut Summon: Knights of Round Terra, Magical Adept Traveling Chocobo Vivi Ornitier Y'shtola Rhul Yuna, Hope of Spira
Some of the top cards are Liliana, Dreadhorde General, Twinflame Tyrant, Doubling Season, Bloodthirsty Conqueror, Sire of Seven Deaths, and Banner of Kinship