Deathvermin

The Deathvermin, also known throughout the Under-empire as the Black Death, are the elite of Clan Rictus formidable Stormvermin regiments and perhaps the most proficient warriors in all Skavendom. They are utterly ruthless and have crushed their enemies in countless battles, much to the annoyence of the Clan's Warlord, Kratch Doomclaw. Indeed, the Deathvermin pose a significant threat to Lord Doomclaw's own powerbase and despite throwing them into hopeless battles on numerous occasions, they have returned victorious every time.

source
Uniforms & Heraldry of Skaven by Neil Hodgson & Robin Cruddace