Lufia 2 [Ancient Cave] - Master Jelly

Oh look! Tia finished him off! Then probably sold the remains.

The Master Jelly is a pretty interesting take on a final challenge. If you manage to reach Floor 99, you expect some kind of superboss and the Master Jelly looks like one. Except that he is not a superboss but the fight has to be won in a very different manner.

You have to deplete the Master Jelly's 9980 HP before he flees and the jelly always moves first. He has 510 AGI so good luck having anyone above that.
First turn: Restores everybody's HP.
Second turn: Restores everybody's MP.
Third turn: Does nothing.
Fourth turn: Immediately flees.
If the Master Jelly flees than the battle is considered lost but not the Ancient Cave run. You are simply not awarded the trophy for defeating him. However, once you obtain the trophy, subsequent wins do nothing. Usually though, a standard AC run is considered complete when the party also defeats the Master Jelly.

The strategy depends heavily on what items were obtained during the descent. There is usually a high enough chance to end up with one or two equipment pieces that provide a fractional damage IP skill. Those are pretty much required and then there is the Gades Blade with its Octo-Strike IP skill. It is also a Blue Chest weapon meaning that once you find it, you keep it between runs. If you have two Gades Blades then a fractional attack followed by two Octo-Strikes can probably defeat the Master Jelly in a single turn.

There is also a sneaky trick or perhaps a bug. Who knows. If you kill your own party before the Master Jelly flees, it is considered a win. Could have been a deliberate secret way to win for people who make it all the way down but realize they do not have the necessary tools to win. However, in Lufia 3 the Master Jelly can no longer be defeated this way.