Farbane is a magical waraxe carved from a mysterious purple crystal. This material makes it exceptionally strong against aberrations, as well as providing its wielder some protection against the same. It is unknown how or where it was created, but it eventually ended up in Acererak's treasure hoard in the Tomb of Horrors, where it was found by the Challengers of the Unspeakable and subsequently wielded by the half-orc ranger Harthur Grai.
During the Battle of Silverstone, when it was discovered that the stone heart of a powerful aberrant monstrosity had been implanted into Boccob's chest, Harthur used Farbane to shatter it and give the former god a merciful death. A portion of their essences was drawn into Farbane, further empowering it. The blade later absorbed additional power from the aberrant parasite within the silver dragon, Orantis.
Though initially thought to have been lost when Harthur fell through a portal to the Abyss, the ranger ultimately returned and gave the axe to the Challengers of the Unspeakable for use in a ritual to close a portal to the Far Realm. The dragonborn Elytra took Farbane with her through the portal and embedded it into the aberrant monstrosity known as Allabar before completing the ritual; though the portal was sealed, Farbane was destroyed in the process.