He has some of the worst stats, both physically and magically. His MP does not exceed 90 to ensure the player cannot cast Meteor with him (Meteor costs 99 MP). Unlike other characters, Tellah's physical stats (save for his HP) actually decrease when he levels up, implying his age is catching up with him, preventing him from gaining strength.
Once Cecil becomes a Paladin(Event), he remembers all his spells especially Curaja, Arise and the "-ga" elementals. He can use Meteor if a Soma Drop or the MP +50% augment is used on him. However, the player is unlikely to see it on a first playthrough since the two aforementioned items are unavailable during the time Tellah is in the party. This can be worked around by hacking the items, by hacking Tellah in the party when the items are available or, in the 3D remake, by beginning a new game plus with the items already in the inventory. Tellah will never be able to cast Holy, Stop (3D only), Quake, Death and Flare.
Tellah has access to the Recall ability, which allows him to cast a random Black Magic spell. Once Cecil becomes a Paladin, Tellah loses Recall in the PS, Advance and PSP versions but keeps the ability to use it in the 3D remakes, which may cast a spell he does not normally have access to. This ability was removed in the North American SNES release.