This blade is a marvel of the swordmakers art. It was forged by the renowned smith Iriactus, the greatest swordmaker of his time. The materials used in the creation of the blade were unique and supplied by an ancient member of the Haarlock lineage.
Two hundred years ago the sword was gifted to Inquisitor Adorjin to aid her in her battle against the daemon Nekaybraianon. However the sword did not kill the daemon, instead it merely imprisoned him, and resulted in the Inquisitors death. At the culmination of this battle the sword was snapped in two, forming the Broken Blade, with its tip lodged into the daemon.
Recently the group rejoined the two halves, and used the sword against the daemon in an attempt to finish it off. An attempt that appears to have worked.
Also later through comparing the blade to The Ice Ring and the lump of metal in The Unopened Box it seems it was crafted from the same Black Metal.