In the same vein as OP:
Lady Amira, Crimson Bat and all the other vampires can 'drain blood' from a Skeleton or daemon. Can't see famine or death being tasty or nutritious to have a drink from.
Hellhound and Kerberos are literally on fire but can get take damage from being burned
Succubus's attack is a kiss and it works on mechs like bast and stean turret. They just can't resist her seductive ways!
Scantily clad characters have an armour rating. I mean, look at the thrall - he's a topless guy wearing some arm wraps and a chain collar! Also those obviously wearing normal clothes, like hag and mad prophet. Not to mention the girls like the devoted.
The general notion of divines/knights and demons fighting on the same team. I mean, priestess and death? Infernal king and paladin? Unlikely alliances, but I like to imagine the stories that could have led to the hero uniting them for a common cause.