FFXII - Espers - Chaos, Walker of the Wheel

Vrishabha Ascendant
Tutelary deity of the scared crystals fashioned by the gods at the time of the Great Making. Created in opposition to Mitron the Chastiser, scion of light. Upon entering the world of Man, he was enveloped in the turmoil rampant there. Lost, he died and was reborn countless time, a walker of life's wheel, eventually to rage against the gods that had so fated him. By sitting in meditation upon the Uneh Pedestal does he clear heart and mind until all that has order and reason and thought is made as nothing.

Previously seen in: the original Final Fantasy as the final boss.

Location: Necrohol of Nadbus, Door of Despair. Of all the optional espers, this one requires numerous subquests just to get the chance to confront him. Counting down the steps:

(1) Speak to "Quiet Nu Mou" (revealed to be Ma'kleou) in Nabreus Deadlands, The Muted Scarp (it's the 2nd area upon entering the Deadlands from the Salikawood, and it has a save point)

(2) If you've completed the Orthros and White Mousse hunts, you'll have the "Blackened Fragment", and the "Sluice Gate Key". Go to Old Dalan's place, speak to Roh'kenmou once to learn of the quest (finding three fragments of a medallion), and a second time to hand over the Blackened Fragment.

(3) With the Sluice Gate Key, go to Garamsythe Waterway, Central Waterway Control. Make sure all the sluice gates are "open" (that is, the light it not on on each Waterway Control). Do the following:

-Close No. 11
-Close No. 4
-Open No. 11
-Close No. 3
-Open No. 4

You should hear a faint "cling"... there will be a shiny object in front of one of the closed sluice gates. Pick it up to obtain the Dull Fragment. Return to Roh-kenmou in Dalan's place and give him the fragment.

(4) -Speak to Filo in South Sprawl (to the northeast of Old Dalan's place, by some crates)
-Go to the fountain Rabanastre's "Southern Plaza" and speak to "Curious Woman" (by the eastern side of the fountain)
-Speak to "Merchant" at Muthru Bazaar, he'll tell you about selling it to an Imperial soldier...
-Speak to Sotted Imperial in Yugri's Magicks; tell him about the woman.
-Speak to Kytes in Lowtown (by Storehouse No. 5)
-Speak to Filo again (same place as before) and tell her you need to see the woman. Choose "Sure, let's go" and you'll be in Yugri's Magicks.
-Speak to Sotted Imperial again... now you got the Grimy Fragment
-Back to Roh-kenmou's in Old Dalan's place, give him the final fragment

That's it for assembling the Medallion of Bravery.

(5) In Archades, go to Charlotte's Magickery in Molberry. Roh'kenmu (not to be confused with Roh'kenmou) wants his Moonsilver Medallion.

(6) In Old Archades, Alley of Muted Sighs (Northeast part of the area), speak to "Proper Gent" (later named Otto). You obtain the Medallion.

(7) Back up to Roh'kenmu, give him the medallion... it will later become the Medallion of Love.

(8) Back to Nabreus Deadlands, The Muted Scarp. You'll have a scene with the three Nu Mous.

(9) You need to return to where you fought the Roblon. Take the secret path/exit in The Slumbermead, go through The Fog Mutters, up to Overlooking Eternity. Once there, approach the shrine. You obtain the Medallion of Bravery, Medallion of Love, and... the Lusterless Medallion? Well that sounds unimpressive.

We're finally ready to begin the process of defeating Chaos. First, gotta defeat his two subordinates, so save your game and head to the Necrohol of Nabudis.

Cloister of Distant Song - Door of Horrors - Examine the depression, use the Medallion of Bravery. Boss fight vs. Humbaba Mistant. You obtain the map of the Necrohol upon defeating him.

Hall of the Ivory Covenant - Door of Loathing - Examine the depression, use the Medallion of Love. Boss fight vs. Fury. You'll obtain the Medallion of Might.

I don't believe it makes a difference on which you fight/defeat first - I assume the first gives you the map, and the second gives you the Medallion, which finally, after ALL this questing, allows you to open "Door of Despair" in Cloister of the Highborn.

Battle info
Status: Protect, Shell, Haste
Weak: Earth, Absorbs: Wind, Immune: Other elements
Steal: Taurus Gem
Attacks: Whirlwind (~8700), Regular (~1500 + chance of Disable), Aeroga (~2500 + chance of Silence), Aeroja (~3500 all + chance of Confuse), Fearga (complete MP loss), Enrage (Atk Up)
Stipulation: Characters cannot Attack
LP received: 60
LP required to learn: 90

Advice: Surrounded by four "Chaosjets" (Lvl 45, HP 4079), each corresponding to a different element. First Dispel (as always), then a casting or two of non-elemental ranged magic like Scathe, or maybe even Scourge, should be enough to wipe them out. Interestingly enough, it seems Chaos takes damage equal to the damage he inflicts with his "regular" attack (though he eventually stops taking the damage, perhaps at HP Critical?). Whirlwind did MAJOR damage and I'm not sure why (perhaps based on a percentage of base HP?), but by now you should (hopefully) have Arise, so use it liberally in case of KO's. If you're having trouble with his assorted wind-based attacks, you might want to acquire some Windbreakers (weak armor but 1/2 Wind damage, sold in Rabanastre and possibly other places.)

Note that you can get around the stipulation of this battle (Attack command is disabled) with the Telekinesis technick. Otherwise, stick to non-elemental magicks.