For the unaware, the Blood War in D&D is the fight between Lawful Evil Devils and Chaotic Evil Demons.
They hate good, but hate each other more.
“She'd become a governess. It was one of the few jobs a known lady could do. And she'd taken to it well. She'd sworn that if she did indeed ever find herself dancing on rooftops with chimney sweeps she'd beat herself to death with her own umbrella.”
― Hogfather