[Illusion]

The last boss is easy, just save your cecil active skill for the end, sephiroth, noctis, then combo.

Cecil gives you a great board, sephiroth enhances everything for damage, and noctis gives that extra combo. So all you have to do is reach 4-5 combos and your set in that short time.

The extra noctis on your team can be used on the floor before that.

... A little too late to give tips for this passed challenge.

Oh and make sure to disable the skill button popouts so you can just click a skill for instant activation, that sheds a ton of time right there on it's own.