Epidemius
Nurgle’s favourite little tallyman. This little fucker is in charge of searching for disease, bacteria, and more of… them..., as well as noting the potency of Nurgle’s new plagues, and coming up with new Interesting new symptoms for Nurgle's new plagues. He is also a lazy fuck, just like his patron, and literally has his own moving squad of Nurglings, being carried around by the cute little shits on a throne. Even as Epidemius surveys and takes notes of the spread of filth and decay, Nurgle knows this, and starts working on some more nasty shit. Because of this, Epidemius focuses on his task even if he takes a power fist to the face, cuz say he were to make an error or untimely observation, Nurgle would probably stop using him as the squeegee for his plague cauldron. He’s even uglier than a Plaguebearer, and the nurglings that carry him also secrete oil. Lovely.
Horus Heresy
He was summoned on Calth during the Horus Heresy, and probably had his arse torn wide-open by the Ultrasmurfs, or Rowboat Girlyman. Poor Epidemius. Nurgle probably stopped using his epidemiusqueegee for a while.