Embyr: The Fifth Age
Blacktongue, Malhun's Knife of Bone and Dark Metal
A wicked blade that serves as a +1 dagger of paralysis/protection from undead.
It is a cursed weapon that inflicts the wielder with whispering voices that cannot be silenced until he/she agrees to a Dark Pact. Once the Dark Pact is sealed, the wielder will be transformed into a ghoul the next time the Dark Blade is used to slay any creature with a soul.
A wielder so transformed can then use the Dark Blade to summon undead as per the spell of the same name.
Any wielder of the Dark Blade (ghoulish or otherwise) can mentally communicate with the mummified remains of Malhun the Seer, but only if Malhun himself desires it.