You can totally fall of the platforms in this fight. That was actually the very first thing I did.
@John During the fight, Ozma takes 3 major forms, starting with:
Sphere form - During the very first Sphere form, Meteor is cast on only one player from each group. The player that's affected has to move away from the group so that Meteor impacts nearby instead of on top of the whole group. After that, Ozma casts Meteor on one extra player. The damage gets pretty severe at that stage. Also on the first Sphere form, Ozma also summons three cube-shaped minions that need to be killed before they inflict a lot of damage on the party. The next time, Ozma will start summoning six instead. This is probably the deadliest form.
Pyramid form - At the beginning of this form Ozma blasts the rectangular platforms BECAUSE FUCK RECTANGLES. To avoid it, you need to move to either side on the circular part of the platforms. During this phase Ozma casts Acceleration, which will cause a lot of damage to your party if you try to move.
Cube form - This time at the beginning of this form, Ozma blasts the outside circular platforms so everyone moves in closer. Ozma will also shoot each parties' tank with a laser and orbs will rotate around the circular platform that damage you while you touch them. You have to be close to Ozma while being mindful that you aren't getting shot by the laser too.
@ 1:40 Ozma begins casting Black Hole and teleports you to another dimension. It sounds peaceful here but it's absolutely fucking not. If you take too long to clear this part, everyone dies! Each party has a demon to defeat before we can progress, but it requires people to stand on a pad to make another parties' demon vulnerable to damage. After that you meet up with all the other parties to fight Ozma again, using Assimilation to encase people in stone if you look at it and casting more Meteors. Once Ozma is defeated here, you can return to the floating platforms where it is stuck in stasis and you have a little bit of time to attack it while it's defenseless.
It's a complicated fight but it's really fun and the boss looks really, really cool.