Terra, Relm, Setzer, and Terra face off agai-- hey, wait a minute!
Yep, there are twelve characters present. And if you kill off every one of them, the game will need exactly thirteen to fill all the slots available. Since the game is a cobbled-together mess of bugs exceeded in severity only by the bugs in the original SNES version, the game goes HEY WHO DO I USE UHHHH YOU COME ON and fills the slot with the first character data it finds. So Terra gets to pull double-duty in this fight, battling alongside herself.
I'm pretty sure there's a fanfiction plotbunny in there somewhere.
Kefka, for his part, has gone six-winged angel. Only two are visible on the sprite, but models done in other media have him with six feathery wings and two bat wings. Eat your heart out, Sephiroth!
Kefka does that screechy laugh again and the final battle begins!
Man with the magic power of two Terras I bet I don't even need all this fancypants equipment. So Terra A unequips...
...and Terra B unequips. Because why have two Terras if you can't duplicate items or watch them make out (and the game does not include spritework of Terra making out with herself).
Kefka always starts the battle with Heartless Angel to drop everyone's HP to 1. So as soon as he gets a turn, he'll do Heartless Angel. He threatens that the end draws near and he's ready to use his ultimate attack, Forsaken, when he's around half HP.
I have two doublecasting Terras, Relm, and Setzer with Fixed Dice/Master's Scroll.
Everyone's at near-full HP. That's not post-Megalixir stuff. Kefka never got to pull of Heartless Angel. I think he got a counterattack off on Relm at one point, but other than that? The final boss never even got to move.
Aw yeah.