Phantom

Phantom is the leader of the Knights of the Round Table, a group of immortal beings who reside in the deepest ends of Undercity Pharos.

He is the only final boss fought in two stories: namely, Ventus and Mythe's.

In Mythe's story, he is the final story boss while in Ventus', he is a story boss preceding the final quest.

Backstory
Little is known about the Round Table, though their presence in Ventus' quest reveals that they have been in control over this world's Undead monsters for centuries. They have also earned the ire of the Arcanians, if the Silver Girl is any indicator.

As A Boss
The Knights of the Round Table are fought first, a total of ten of them, with three of them being fought twice. As the Knights are varied and fight in myriad ways, the party must have a varied arsenal of it's own. (Shields and/or Reflecting weapons are practically a requirement) The toughest enemy in the bunch is the Axe Knight, capable of dishing out a lot of damage in little time.

Once the ten are defeated, the player fights Phantom.

Phantom is capable of destroying an entire party in no time, so only advanced players should attempt the fight.

LP-Draining techniques such as the Spear's "Acupuncture" and the sword's "Bopeep" are required to even be able to damage him properly. His attacks may also cause the "Paralysis" and "Confused" ailments. Just for that little extra something, he is very fond of chaining his attacks in combos. so this fight is completely based on luck and preparation.

Note that Ventus has a much higher chance of winning the fight with little casualties, since he can power up indefinitely from Carrier jobs and the power of the Dragonheart's "Ultra Heal" ability. Mythe players must expect retries, and know the game's systems better than they know themselves in order to stand a chance.

Battle Quotes
Starter: "You dare attack us with your mortal weapons....? .....Fools!"

First attack: "Die!"

After five turns: "You fail to understad the futility of your own existence. Fools!"

After defeating the Party: "Hahahahahaha......."

Defeat: "We are immortal.....We are immortal.....We will continue to exist....Forever....."

For all the lines of the character, go here: http://www.youtube.com/watch?v=gG1ywWRXjv8#t=4m33s

Trivia

 * Phantom's voice suggests that he is a collection of the conciousness of the Knights of the Round Table, (Since he sounds like multiple people when speaking) possibly making him their ultimate form rather than their leader, but one can merely speculate. This is further supported by the fact that he refers to himself as "Us" (Meaning the Knights) rather than by name.
 * Considering how Alyce Ambrosia is likely a reference to Merlin, it is possible that Phantom is meant to be an analog for King Arthur, but allas the game doesn't deliver more information regarding that.