Deus

Items found at Deus:G-Godson Ammo, Pilot Shield

To the West of Bart's Hideout is a dot with a Grey formation (Deus). Enter it, and head North and a passage will open, so go inside. Head North, turn NorthEast, then North, jump the laser, then head NorthEast up the ramp. Turn SouthEast, then NorthEast jumping the Laser and head North to the next area. Dodge the lasers while falling and jump off the pillar when you reach the next area. You can see the exit to the NorthEast, but not reach it. Go down the elevator just below the pillar, head South and circle around to go up into the next elevator. Head SouthEast, but don't use the elevator, jump twice to the top of the pillar instead. Check it and the bridge to the North below will move to the East. Go down the elevator, head East, then take another elevator up. Head North, down the elevator, turn NorthEast, then jump up the pillar and check the light to switch another passage. Head back to the first switch, then go NorthWest, SouthWest and SouthEast to reach another area. Head South, turn East, then North back to the previous area. Get the G-Godson ammo behind the pillar and head back South until you find a crossroad, turn SouthWest and turn again South to go back to the other area. Go SouthWest and up the first elevator you find, turn East and jump at the top of the pillar to turn another switch. Head back West, go down, then SouthWest, up again, then South. Skip this paragraph from now on if you just want to reach the final boss. Turn SouthWest, then South, then SouthWest again to find a Pilot Shield. Now go back to the spot before skipping the paragraph.

Turn NorthWest from the last spot, then North to the next area. Head SouthEast (There should be a passage now), then go down the elevator, head East, then jump in the gate. After dodging more lasers, you'll be at the place where you fought Amphysvena and Opiomorph. Head East first and talk to Johnny if you want to buy something or leave the place. Upgrade if you forgot to do it before and head back if you're ready. Save your game, choose your party to fight Deus, then head North 3 times and jump inside to find Deus. I suggest you destroy each of the orbs (Although you can beat Deus without doing it), and I'll explain how to identify each of the orbs. Each orbs emmits a certain colored light. To fight Harlute, check the blue one; to go against Marlute, the yellow one; against Metatron, the gray one; lastly, to fight Sundel, check the pink light (It's up to you which boss to fight first).

Note, that you should save Fei for the last battle as your allies suggest. To fight Harlute, equip Speed Shoes, Holy Pendants and GNRS 50, then start attacking him. Harlute will causes many status effects changes and he will freeze 2 of your gears for a certain period of time. It's a tedious battle but it won't take much strategy to win. To fight Marlute, bring Chu-Chu (So, the little pink puff has some after all...) and equip your gears with Z Chargers, Frame HPs and Tank Guards. You can't use gear deathblows (Luckly, weak triangle attacks take good damage) and Marlute will use a powerful attack against all gears sometimes, but if he can't drain your fuel, you have all the time to heal back and re-charge. Like all other bosses, it only takes patience. Metatron is a pure beat-em-up battle, keep attacking him and healing until he's down (He'll take lots of damage, so use fully-prepared gears that you don't want to use in the last battle). Lastly, Sundel will start the battle "choosing" one of your gears. Whatever you do, do NOT attack Sundel with the chosen gear (Most likely, you'll have to heal or charge since every time you attack Sundel with the other gears, he retaliates at the chosen gear). Also, this battle may or may not takes lots of patience, depending if Sundel decides to use his healing every turn (Yes, he does that). After you're done with the 4 guys, bring Fei, equip everyone with Speed Shoes, Holy Pendants, Anti Angel Systems (Power Seraphs drop those), Frame HPs and either GNRS 50s or Z Chargers. Note that Deus can damages every gear for over 12000 HP, but if you defeated all orbs, he won't many skills (like the irritating healing) and have less HP. Just don't let your HP too low and keep attacking him until he's down. After another scene, Xenogears will be restored and you'll face the last boss!

Finally, the last boss. Urobolus can take 7000 HP in one attack, so heal when necessary. I'd suggest you to keep using X, Level 1 Deathblows; This battle is a sinch compared to Deus and the orbs. It'll take a while, but you'll eventually win and finish the game! Congratulations!