Background: Xannel is the being of depression, or who was once the spirit of Pandora's Box, so it seems. Now she's given most of her feelings away, but unlike the old Pandora's Box story, she kept one more feeling-- depression. The feeling where human beings can do no more. Zeru stated in the chatbox that Zure once knew Xannel. Xannel had been sealed here for 203 years, feared for her power. She is the daughter of the God of the Underworld.
HOW DO I FIND XANNEL?
You must have finished Melody and Nayu's Saga and have beaten the Goddess of Tempest. Or, at least, be able to access her map. Xannel will be in another portal, leading to the "Sealed Chamber." See my Extra Saga guide for more info on this.
Say hi to your death!
Speed: I don't know; invisible ATB sprites (Clever, Zeru!)
List of Attacks: Xannel: Omega Dragon Crusher 1k-2k damage on party
Blood Bending* "Sky": 4k penalty
Blood Bending "Behind": 5k penalty
Blood Bending "Ground": 2k Penalty
Hold ??? on second hit: 3k Penalty
I have yet to see a forward Blood Bending, but it probably exists. Be on guard.
Xannel's Will: Hei-an Stance
Despair: Miserable Fate (Will only use if Hei-an Stance is casted.) Will kill you unless you have the "Light Aura" buff
which is obtained from the "Amulet of Hope." Yes, I survived it.
Calm Soul: "Cold Wind" (SR -> 0%)
Healing Arts "Salve": Heals around 25k. Less annoying than Tz back in FSI, but still annoying.
Light Magic: Dispel: Removes all buffs
Xannel's Second Form (Get Xannel to 50% HP)
She will use Blind at the beginning of transforming.
Once you hit 45% HP on this form, she'll automatically remove blind with Heaven's Judgment.
All of her above Blood Bending attacks.
Blood Bending: Press ??? on second attack: 4k penalty
Illumination: Heaven's Judgment: This gets rid of Blind (Thank you.) and does some mediocre damage.
Elixirs, if you're not very strong.
* Explanation of Blood Bending. It is the same as the "Hold" attacks. For example, if she uses "Blood Bending: Sky" and you don't do anything, you'll get hit pretty hard. However, if you hold the corresponding key (Up) then you'll be hit for 1 damage. For the Press ??? on Second Attack, keep a close eye on the direction of the first attack before pressing the key of the same nature.
Example: So, for the first attack, the red lines point right. Hold right.
For anybody that's lazy and can't figure stuff out, here it is:
Forward: Left (If it exists...)
Strategy: Get rid of the spirit ASAP. You'll have a much easier time dealing with Xannel's second form if you do. If you can't do more than 25k damage in a turn, why are you fighting her?! Xannel is very fast, so don't underestimate her speed. After that, get rid of Xannel herself and be happy and joyous and smile and laugh and frolic and.....yeah.
EDIT: SR? Xannel? Hahahahaha no....But the Spirit can be hit by it. I wonder if Zeru intended to do that?
99999 Form 1 (50% for form 2)
99999 Form 2
1 Xannel's Will
Defense Rating: Form 1 and the Spirit have more DEF than the average enemy. Less than Ninto and such, but still considerable. Form 2 has higher DEF than Form 1.
Rewards: 105,000 EXP and 20,000 Mesos
Infinity's Sword Cannon (Only once)
Infinity's Sword Cannon is the strongest gun(blade) in the game, for Lenna. Boasting an attack power of 203, it is quite the force to be reckoned with. Also, if you use the "Attack" command, it will hit three times.
Closing Notes: Xannel isn't called the hardest boss for nothing. Best of luck to you, and make sure you're well trained!