Star Ocean: Till The End Of Time

The Maze of Tribulations is a post game dungeon accessible from the Mining Town of Kirlsa. Head to the southern part of town down into a mineshaft, at the dead end use the Ring of Disintegration to open up a path that will lead to a transporter: get on the transporter to be taken to the start of the Maze of Tribulations. I highly recommend using this comprehensive FAQ to help guide your way through this dungeon (Credit to Alex for the FAQ). This dungeon is relatively short, in comparison to Sphere 211. Once you reach Level 8 and defeat the other enemies, you will face off against Gabriel Celesta.

Gabriel Celesta Breakdown:

Gabriel's Level: 114
Recommended Level: Early to Mid 90's

First thing's first, item synthesis for this fight is nearly a must. All of your party should by now have the second best armors and weapons in the game, with Orichalcum's and maybe a few Boots of Prowess on there as well. With this boss fight specifically, you'll want to have an Amulet of Freedom synthed onto you weapon as well: as Gabriel uses many attacks that paralyze, and you don't want to compromise defense by equipping the amulet as an accessory. When you damage Gabriel enough he'll start using a Dragon attack that covers nearly the entirety of the area. You'll want to dodge it by staying around the outer edges of this area. As far as Battle Skills go, you'll want equip the strongest ones you have for each character: notable ones include Energy Burst for Maria (scroll found in this dungeon) and Infinity Kick for Cliff (Fayt's Side Kick also works very well in this fight too). Overall, so long as your party is properly leveled and have protection against Paralysis: this fight won't be too difficult.

Once you defeat Gabriel Celesta, you will unlock the trophy. (You can go back and fight Gabriel at any time, so you don't have to worry about the BT's during this fight)