5e Forgotten Realms Hell lore?

Howdy hey girls and guys!

I need help on my knowledge of the Forgotten Realms and the demons and devils in the 9 hells (I believe it is). Are there any lorebooks on that?

I've been DMing for about 2 years now and I'm currently DMing Dragon of Icespire Peak with my college friends. One of my players is a war cleric who's a bit evil. And he worships this homebrewn devil/demon (I honestly can't decide yet but maybe he's both?) named "D'burah the demon King". And basically his whole deal is that he used to be this small Lil imp who was named "D'burah the demon kid" and he used to be real weak until he started killing other demons and eating them to absorb their power. I want there to be this moment where he's listing off the BBEG devils that he's killed/overthrown and absorbed their power and I want it to be intimidating and metal and shit but I pretty much only know Orcus lol. I was thinking I could also name off Asmodeus and Beazlebub but idk if I wanna mix lores like that (even tho my Players are naturally doing it on their own but I mean that's my problem not theirs). So his plan is to get his followers to gather these materials to summon him with this giant spell/incantation/whatever so he can wreak havoc on the Forgotten Realms. One of the things required, being the soul of a dragon (Cryovain).

My players have also gotten in trouble with the law, as they were under suspicion of arson, murder, and kidnapping (homebrew shit) and now they're definitely in trouble as they have killed a couple of the knights of NeverWinter. I kind of put myself in a rough spot because I had the Inn keeper of the stonehill Inn say to the party that he can't host the party at his Inn anymore because it's not safe anymore and bad for his business. But now I'm like, well where are they gonna long rest now? Shit... fuckk... DX

So yeah tl;Dr I need to know what/where the BBEG devils and demons are and maybe lore about the gods and angels in heaven or whatever would be good. And lore on the sword coast in general would also be neat. So are there any lorebooks for those things?