Xan's moonblade

This Moonblade (Moonblade +3 in EE) is a powerful magical sword. When unsheathed, the blade will be engulfed in blue flames, very similar to The Burning Earth. It can only be used by Xan, who was chosen by the sword itself to wield it. It falls under the Small Sword proficiency in Baldur's Gate and Dagger in the Enhanced Edition.

The blade offers a bonus to the Armor Class of +1, a THAC0 bonus of +3 and +50% fire resistance to the wielder. It can inflict 4 – 11 slashing damage and has a speed factor of 2 (though the classic version of the game states in the sword's description only a factor of 5).

It's found in Mulahey's chest in the Nashkel Mines, on the fourth level. Xan is held prisoner nearby.

Description (in game)
“''This potent weapon was created by the smiths of ancient Myth Drannor. Moonblades are used in the long process of selecting a ruler for the isle of Evermeet. A Moonblade chooses its owner, and in the case of this sword it has chosen the elf, Xan. Only Xan can use this blade, anyone else who tries will find themselves unable to lift the sword. This particular Moonblade gives resistance to fire and gives its user a bonus to his armor class.''”