Morgana's Enchanted Sword

"You cannot overcome it. It will fight to the death."

- Guinevere to Elyan

Morgana's Enchanted Sword is a sword enchanted by Morgana to guard Guinevere. It is able to hover in the air and attack on its own.

History
Morgana enchanted the sword when she kidnapped Gwen and held her prisoner in the Dark Tower. When Arthur, Merlin, and the Knights of the Round Table arrived to rescue her, Morgana left the sword to guard her as part of a trap to kill Arthur.

However, it was Elyan, not Arthur, who found Gwen at the top of the Tower. Though she begged him to leave her and save himself, Elyan engaged the sword in a duel and managed to defeat it by tricking it into lodging itself in a window shutter. Unfortunately, he was stabbed in the process and died soon afterwards in Gwen's arms (The Dark Tower).

Trivia

 * Gwen's assertion that Morgana enchanted the sword to protect her is the first indication that they have become allies (The Dark Tower).