This is a story line achievement and can't be missed.
Emperor of Fire
HP - 3800
EP - 11000
Element Type - Fire
Blow Crusher - a sword attack that hits 2 complete rows, 8 squares altogether.
Hell Fire - fire based attack that hits 6 squares, 2 in the middle and 4 behind (basically a row and a half)
Restoration - heals him
Act Unit - not an actual attack, makes the blue light appear
Melt Unit - not an actual attack, makes the blue light disappear
This can be a hard battle if you don't pay attention. If you attack him while the blue light is above his head you will hurt/kill Karen and lose the battle. You can only attack after he uses Melt Unit and the blue light disappears. He also regenerates about 100 HP and 200 EP per turn. His attacks can be devastating doing about 300-500 per hit. He takes up four squares on his side of the grid so you can spread your team out so that when he attacks he only hits 2 of your party members during his attacks.
Atsuma's fire attacks don't do a lot of damage being that the Emperor of Fire is also a fire element. But his EX attack Stun Bead Flare will still do around 500-700 damage depending on your parameters/level. Have Raigar use Levatain to boost his attack power for more damage. When Act Unit is in use (blue light) have your characters heal or use buffs, or put them in standby. If you have the golem Maran Glave (obtained from the Casino) his aqua attacks do a lot of damage to him (did about 1000 with Aqua Impulse).