The Adventures of the BMBH
The Orcus Blade
A Ritual Dagger
The Dagger was forged in the Shadowfell. The BMBH found it while exterminating some Kobolds.
Vomitrius took an immediate shine to it. Especially when it was discovered that it destroyed the body and held the souls of anything killed with it. Also it sounded like the High Priest of Orcus, Kalarel might have wanted it to help open a rift to the Shadowfell.
Eventually the soul of Kalarel was imprisoned in the dagger, and it may or may not have exerted some minor influence on the townsmen Fergus and Ciaran. In the city of Illian it was decided the dagger was not helping the already chaotic situation and they tossed it back to the Shadowfell.
A few days later they realized that may have been premature, as the Raven Queen had coerced them into a mission to destroy the Shadowfell. Something the dagger could accomplish.
So they had to haul ass to the Shadowfell and get it back. But the old Lich Malphas had gotten it first. Realizing what they intended to do to the Shadowfell he decided it was wizer to have his wife escort his phylactery off the plane. Which the party consented to.
The dagger destroyed the Shadowfell. It now remains in the hands of Vomitrious, who claims to have control over it.