Via Infinito

A 100-level semi-random dungeon hidden in Bevelle. Was discovered by the Kinderguardians. It's said that every type of monster, known and unknown, resides within. At the end, lays Trema, the founder of New Yevon. Getting to Trema is a great ordeal, as he is guarded by many godly fiends.
B10: Elder Drake. Extremely fast and even better strength.
B20: Aranea, a giant crab/spider. Not overly strong but can easily Stop your entire party instantaneously. When oversouled, it likes to eat people and spit them out at high velocities.
B40: Black Elemental, the strongest know Elemental being. It's EXTREMELY resistant to magic and physical damage and has an even better magic attack. It uses every known magic, including Ultima.
B50: Mega Tonberry. Very, very fast has an Immense Attack. Is like a normal Tonberry, but 100 times better.
B60: Concherer, another crab/spider. Overly beefed with strength and defence. It's Megaton Press is said to crush even the gods. It likes to spit gunk at people to drain their mind powers.
B80: Chac, a giant Baslisk. It will change all it looks at with it's Stony Glare. After turning it's victims to stone, it has a habit of casting Heaven's
Cataract to completely obliterate the stone person into nothing but a few pieces of rubble.
The final 19 floors houses all of the past godly fiends and in great numbers. They roam the halls up until Trema. Trema is guarded by the a god among Weapons, Paragon. It likes to use Genesis after attacking, which is good enough to wipe anything out in it's path. One it gets weaker, it tends to defend itself with Ultima spells. It usually counter attacks with a spell known as Final Impact, taking off portions of people's health.
Trema is a true god it would seem, as he throws Demi, Flare, Ultima and Meteor spells at his oponents on a regular basis. His magic is the stongest magic known to any living being.