Rumors had reached the Avatar that Lord Blackthorn possessed a special sword, stored in a chest covered in human skin, deep within the bowels of the Palace of Blackthorn. The forces in this sword were said to be so horrible that it would force the wielder to slaughter his or her own friends in a fit of madness. The wise Avatar resisted the temptation to wield this horid weapon.
It is unknown what later became of the sword.
Another of the Oppression's playthings of Evil, the Sword of Chaos possesses the soul of the knight who wields it. Once the Sword is brought to bear, its wielder will seek to slaughter his or her allies in battle. Blows of unmatched strength will be struck until each and every friend suffers a bloody death, whereupon the insane fighter will faint dead away at the sight of the carnage. The Sword rests in a northeastern chamber of Blackthorn's palace's ground floor, within a box lined with human skin.
- According to the Prima Guide to the Ultima Collection, the Sword of Chaos has a 99(!) damage rating, which is equal that of to a glass sword.
- The Chaos Sword disappears after the first time it is used in combat.