Biologus Putrifier

Its like Mengele just fucked a living, breathing Ebola Virus and this was the end result of their sweaty lust.

Biologus Putrifiers are a type of mutated warrior of the Death Guard. Judging by their name and role, these maybe the corrupted Nurglite version of the Techmarine of the Adeptus Astartes, more specifically, they are the corrupted Techmarines who specializes in the subdivision of the biologi and xenobiologi section. You would think 40k already have enough mad scientist tropes to bring on the table. These chaps are the refiners of the diseases created by the Foul Blightspawn.

Overview

Biologus Putrifiers like their symbiotic kin, the Foul Blightspawn, bear a unique mutation: lidless eyes that grow like cysts concealed beneath their flesh. Known as occulobes (apparently GW's writers forgot that the name "Occulobe" already belongs to one of the Space Marine organs), the gaze of these can even penetrate armor to perceive every aspect of an infection’s spread through a body. That's right, they literally have cancervision.

They then quickly record their observations, creating potent tomes of forbidden lore. Driven by an obsessive desire to test their plague-batches to perfection, Putrifiers take a very active role in spreading disease upon the field of battle, observing all aspects of plague and disease they encounter.

Yet to simply observe is not their only duty. Samples must be extracted, and tests must be run, and for this they are armed with their Injector Pistols, which create a sick and agonizing death. Those specimens whose deaths are especially fascinating are pierced with injector pistols once again, this time to extract whatever clotted foulness now passes for their blood, ready for later study. The end results are refined again into especially potent blight grenades, which they carry in large racks that they are all too happy to share with their comrades. Outside of his usual armaments, the Putrifier is also armed with a Plague Knife for self defense and somehow maintained his Mark III: Iron Armour in tip-top shape.

Due to their deadliness, Putrifiers are often targeted on sight by the enemy. Yet should a Putrifier be struck by sufficient firepower or a powerful enough blow, the attack is liable to rupture his racks of blight grenades... Whoops!

Crunch

In 9th Edition, they have the same stats as the Foul Blightspawn. He's only got a plague knife for melee, and his shooting leaves much to be desired - sure, his Injector Pistol is S4 AP-1 D1 and deals 1d3 mortal wounds when it wounds Beasts/Cavalry/Infantry, but it has a pathetic 3" range. It's his grenades that make him worth it: his Hyper Blight Grenades are AP-1 and deal 2 damage, and any other friendly Death Guard units within 6" get their blight grenades upgraded in the same way. As an added bonus, when killed he explodes like a vehicle on a 4+, inflicting a mortal wound on any non-NURGLE units within 7" of him. He also buffs your melee: 1/turn at the start of your charge or any fight phase, pick a friendly <plague company> core unit within 6" - until your next command phase, that unit's melee attacks with Plague Weapons deal 1 mortal wound on nat 6s to wound.