I begin this play through at the beginning of the Jade Pass on the over world which is the last savable area before the emperor. After a run through this dungeon, I arrive at the Pandemonium Castle which involves a lengthy climb to the ninth floor where the emperor resides. At this time I equipped my party members with three elixirs, encase the battle lasted longer than expected, and five crosses, because the emperor likes to get a little trigger happy with the curse 16 spell. You will note that most of the treasures have already been obtained from a precursory trip to plunder the castle.
The emperor has some nasty vampiric attacks that he uses to steal HP from your party and give it to himself so I learned not to osmose the emperor and try to keep him using magic based attacks as long as possible. Granted my party members could have stood some more leveling up, because the damage they inflicted on the boss was less than effective, but I found that the best thing to do was to level up the following spells to at least level 4: haste, shell, aura, berserk, barrier, blink, shell, and wall. I basically have these spells staggered across all characters so you can effectively get your buffs up quickly and the level is so the spells have a good chance of sticking when only cast once. As you see in the video, my first couple rounds as used providing buffs to all of my party members. This is mostly to lessen the damage they take from magic and also get them in a state to be immune to the emperor's physical attacks when he runs low on MP. I made sure spells that will be cast multiple times were given to characters which were not likely going to be participating in a physical assault, namely Maria, who had blink.
I start off but getting aura, berserk, and haste set up along with the bonus shield, wall, shell, and barrier spells. Then after those stuck I basically just continuously attacked with my fighters while continuously spamming my party with blink spells. The awesome thing about blink on this game is that the evasion was cumulative with each cast. This means eventually you reach a point, as seen at the end of the battle, where your evasion is so high that the emperor cannot land a blow. This way he cannot inflict damage and, more importantly, replenish his own HP in the process. Towards the end all of my fighters were just dishing out damage while Maria was casting blink every round. I was surprised how well this worked.
After the battle the ending plays through and the credits roll.