Plague Marines are those Chaos Space Marines who have wholly dedicated their lives and souls to the service of the Chaos God Nurgle.

Within their corpulent and disgusting power armour their bodies are bloated with disease, swollen with corruption and rank with decay even as they no longer are capable of feeling pain, the greatest mutational "gift" given to them by the Plague Lord.

Pestus is no different, his "gifts" having turned from bloated flesh into gross slimy tentacles sprouting from all over his body.

Although he wasnt "blessed" by choice he still accepted what he had eventually turned into, using this new found power to fuel his twisted, leperous, self indulged ways.

https://rule34.paheal.net/post/view/884661#search=Nurgle

https://rule34.paheal.net/post/view/1758058#search=Plague_Marine

https://rule34.paheal.net/post/view/1758040#search=Nurgle