The Fell Arms (魔装具 Masougu?, "Demon Clothed Tool") are a series of weapons similar to the Devil's Arms in Tales of Symphonia and Six Catalyst Weapons in Tales of the Abyss. Legend in the Empire says they were spawned by a fourteen-headed monster, while the Krityan legend states they were made at the height of ancient blastia civilization as special weapons of untold power. Fell Arms resonate with each other, meaning that once one is obtained, it is possible to discern if another is a Fell Arm.
Once the party obtains "Abyssion", they decide to gather the rest, deciding that it would be better for the party to have rather than for them to fall into the wrong hands. After obtaining all seven of the weapons, the party attempts to hand them off to Flynn Scifo but decide that he is too busy to deal with them, so they keep them. If this cutscene is viewed, then after defeating the final boss's second form, Dein Nomos and Tarqaron will react with the Fell Arms to unleash their true power. While unsealing the Fell Arms, they also provide the final boss with a third form, titled the "Radiant Winged One". He says that he has the ancient king of the Entelexeia on his side, as well as Terca Lumireis itself. In the PlayStation 3 version of the game, the ancient king of the Entelexeia is revealed to be the Spiral Draco, who is immune to the Fell Arms.
The Fell Arms increase in power based on how many enemies that character has killed on the current playthrough. Unlike the Devil's Arms and Catalyst Weapons, it is possible to see exactly how much the character's stats have increased. Also, once the ability to fight the "Radiant Winged One" is unlocked, it will remain unlocked for that playthrough every time the final sequence is initiated, meaning it is possible to obtain an infinite amount of copies of the unsealed Fell Arms.
The Fell Arms consist of the following weapons:
- Abyssion (アビシオン?) and the unsealed Blazor Edge Abyssion (紅蓮剣アビシオン Gurenken Abyssion?) - Yuri Lowell's Fell Arm, taking the form of a sword. After rescuing Estelle from Zaphias, it is possible to go to the Elder's Residence in Myorzo to trigger a scene where the Elder will introduce the party to the Fell Arms and give them this sword. The party mentions that it give off a similar feeling to the Dein Nomos.
- Zarich (ザリチェ?) and the unsealed Sand Spear: Zarich (獄砂槍ザリチェ Gokusasou Zarich?) - Judith's Fell Arm, taking the form of a spear. After converting four Entelexeia into Spirits, the spear can be found at the aer krene near Nordopolica. Upon approaching the sealed entrance, Abyssion shines and releases Zarich, subsequently providing access to the aer krene within.
- Nebilim (ネビリム?) and the unsealed Infernal Angel: Nebilim (神魔弓ネビリム Jinmakyuu Nebilim?) - Raven's Fell Arm, taking the form of a light bow. After obtaining the Sorcerer's Ring Level 4, the bow can be found in a chest in Keiv Moc behind foliage that must be burned with the upgraded ring.
- Mercurius (メリクリウス?) and the unsealed Soul Blade Mercurius (霊剣メリクリウス Reiken Mercurius?) - Estelle's Fell Arm, taking the form of a sword. Again requiring the Sorcerer's Ring Level 4, the sword can be found in a chest in Relewiese Hollow, behind a pile of rubble which needs to be destroyed with the upgraded ring.
- Glasya Labolas (グラシャラボラス?) and the unsealed Wrath Bringer: Glasya Labolas (憤激斧グラシャラボラス Fungekiono Glasya Labolas?) - Karol Capel's Fell Arm, taking the form of an axe. Also requiring the Sorcerer's Ring Level 4, the axe can be found in the Quoi Woods, in the same area as the Giganto Monster "Chimera Butterfly", which is blocked by vines requiring the ring to burn down.
- Susanoh (スサノオ Susanoo?) and the unsealed Blade of Sins: Susanoh (大罪剣スサノオ Daizaiken Susanoo?) - Repede's Fell Arm, taking the form of a dagger. It is obtained in a chest in Tarqaron, in the same room as the "Uroboros".
- Uroboros (ウロボロス?) and the unsealed Calamity Chain: Uroboros (凶鎖刃ウロボロス Kyousajin Uroboros?) - Rita Mordio's Fell Arm, taking the form of a whip. It is obtained in a chest in Tarqaron, in the same room as the "Susanoh".
- Nanatsusaya (ナナツサヤ?) and the unsealed Shisoken Nanatsusaya (始祖剣ナナツサヤ?lit. "Originator Sword Nanatsusaya") - Flynn Scifo's Fell Arm, taking the form of a sword. It is obtained in a chest in the Telescopic Graveyard.
- Kurubis (クルビス?) and the unsealed Kokontou Kurubis (狐魂刀クルビス?lit. "Fox Spirit Knife Kurubis") - Patty Fleur's Fell Arm, taking the form of a knife. It is also obtained in a chest in the Telescopic Graveyard.