The D&D 5e Monster Manual is probably the best Monster Manual ever made for the game

… and yet it can hacked, updated, modified, and otherwise screwed with in many fascinating ways, which is what Zak's doing right now. Following his awesome Old One-ification of the Aboleth, he's on to Angels, and it's good, good stuff. I particularly like ranking the things based on old Hebrew lore.

Playing D&D With Porn Stars: …and Gygax Saw The Angel
Angels (split into deva, planetar and solar and all barely distinguishable) come right after the aboleth in the manual and have a similar problem–since they, too, strongly rely on a monotheism for their impact. Plus they’re good which means there aren’t a lot of reasons to fight them.