This is a really great idea. The challenge for the PCs is trying to navigate past these strange creatures and their temptations. Perhaps each of the Demon Lords exhibits one of the 7 deadly sins (to give some thematic thread?) And their goal is not to kill the PCs but to simply tempt them into remaining with them in their lair.
I'm actually going to break down this villains even more just for kicks;
- The Drow are cartoon fascists; think the Red Queen, Scar in the Lion King, the grasshoppers from Bug's Life. Their bad, and will kill you, their self-absorbed, think their superior. Clever and smart, but quick to underestimate you. But nothing more than that.
- Baphomet is the lord of the wild, pure wild abandon. He'll try to convince and show the players that rules and formality is for the weak and meek. Why eat your vegetables and say "please and thank you," when instead you can eat ice cream and make fun of those you don't like? He's an evil version of Baloo from the Jungle Book.
- Demogorgon is pure, unadaltured rage and temper tantrums. Not only are you right to feel angry, it's the anger that makes you strong, the rage that gives you power. You deserve your revenge. He's the classic Sith "hate leaves to the dark side, which leads to suffering," trope.
- Fraz-Urb'luu is here to trick you, solely because he enjoys it. He's your friend, he's your worst nightmare, he's constantly changing and filling your mind with doubt as to who is your friend and who is your foe. Sometimes he'll help you, sometimes he's leading you to your doom. Mixture of the Chesire Cat and Mysterio.
- Graz'zt is every negative trope about love; he's lustful and self-obsessed, and wants you to love him because he's the only one able to love you back just the way you need it. He's everything you want in a partner, except you've got to be totally devoted to him and no one else. Flips genders for whatever is necessary. He's every seductress trope wrapped into one.
- Juiblex loves to eat and consume. He should sing just to give him a little more whimsical, but his whole drive is greed for food, preferably candy and cake and everything nice.
- Orcus is a popularity hoarder, as he wants to be the center of attention. His way of doing that is raising a horde of skeletons and zombies, who all tell him how great he is. Either you got to get with the program and tell him how good he is, or there's something wrong with you. If there is, you need to die and get raised back to be "fixed." Regina from Mean Girls.
- Yeenoghu is a the king of laughs, always thinking he's funnier than he is but having a joke and pun primed for every occasion. Watching people get hurt is of course the highest form of comedy, and the more chaos there is the funnier the world. This is the Mark Hamill Joker.
- Zuggtmoy is a clinging, nitpicky mother. She knows best, and if you disagree you need your mind wiped clean for your own safety. Everyone just needs to slow down, breath the spores deeply, and good old Zuggtmoy will take care of it. She's the snake from the Jungle Book, mixed with bad-mom vibes.
