The Fellblade

 is a weapon item added in Total War: Warhammer II.

Description
The sword of swords, created by the Skaven to destroy the greatest Necromancer to ever walk the world. It is a doomed thing.

A toxic artefact constructed with warpstone, the Fellblade was given to Alcadizaar, the last living King of Nehekhara, when the Skaven freed him from Nagash's prison. With it, Alcadizaar slew Nagash, before succumbing to the blade's toxic effects and dying. Sadly it was too late, as Nehekhara had already become a land of the unliving through Nagash's great spell.

The Skaven burned Nagash's body and melted his bones, but his hand crawled away...