Before I post the full scene, decided to just put up the standalone character, who's the Death Brigadier light-flamer specialist, Reez the Cheerful.
Like many of the BloodPacters, Reez got his nickname from the most evident behavioral trait, and indeed, you'd be hard pressed to find a more friendly, cordial and uplifted follower of the Blood God. And Reez is quite sane in his cheerful spirit - not a giggling madman, but a functional team member that just sees the brighter side of things though his permanently-affixed goggles in the grimdarkness of the far future.
The promethium fumes and burning flesh oils just make him high.
Reez was to be one drawn for the Penal Legion for his insubordinance, pranks and lulzing in the Cadian regiment he was enlisted to too - a place unfit for someone with his penchant for humor and laughs. But the prospect of death in the Penal troops made him turn his weapon on his former comrades, which he took as fitting irony. Now, making BBQ out of Imperials is the way he repays the Pact for allowing him to look at burning people and laugh.