Nightbringer
Nightbringer is a sentient longsword. Formerly wielded by Zirithian - a drow who sought to become an exarch of Orcus - it was claimed by the Challengers of the Unspeakable upon the death of its owner. Orcus appeared and demanded the blade, but the sword spoke to them, urging them not to give it to the demon lord. When it promised Harthur Grai the power to slay his foes in combat, the ranger decided instead to keep it for himself.
It is unknown who created Nightbringer, but it insists that it was merely found by Orcus, not forged by him.
Properties
Nightbringer speaks aloud in a hoarse whisper, and exhibits a certain level of awareness of its surroundings. It grants its bearer protection against undead creatures in combat, and is capable of taking control of weaker undead.
Perhaps its most notable property, though, is that it absorbs the souls of creatures killed by it. What happens to these souls, and how Nightbringer benefits from them, is unknown; Nightbringer, however, is always very eager to do so - and the stronger the soul, the better. Two of the more notable souls it has recently absorbed are those of the Matron Urlvrain, ruler of the drow city of Phaervorul, and the the red dragon Rukaleth.