Now DnD seems to have slipped into the mainstream consciousness and my kids are interested again in adventuring in the World of Greyhawk, it's re-kindled my own grognard love of the original game. I will admit that it gave me a buzz when the lads slapped down a miniature of the 'demogorgon' on the tabletop in the introduction and entered into the discussion of defence versus assault.
Now die-hard OD&D players such as my grey-haired self would never presume that the mighty Prince of Demons would be vaguely concerned about a Fireball. After all, demons take half-damage from fire, and the Prince has 95% magic resistance, so you'd need a 20th level magic-user to have a 50/50 hope of actually sizzling him, and then he'd need to fail a save to take even half of the 20d6 damage!
I've been fascinated by Demogorgon since I first bought the Monster Manual in 1983. The characters in my various campaigns over my teen years never got close to the power level needed to trouble him (my brother Dan's characters took down Lolth in Q1, but this is a different level). And when you look at him, he really is the toughest bugger in the original MM:
200 hit points; AC -8, needing +2 weapons or better to hit (not that you'd be coming near him with anything less than a Holy Avenger); the aforementioned Demon saves and magic resistance. And whilst you're trying to chop him up as your mage sobs like a little girl in the corner, he gets some beast powers back...
He has two mandrill heads, which together use a hypnotic gaze which automatically mesmerise you if you're less than 15th level/ hit dice. The individual heads can beguile, or cause insanity. The Demogorgon's tentacles do a measly d6 damage with a rot that makes arms drop of in 6 minutes (with a quarter of the hit points), and the tail drains 1-4 levels. Ouch.
If so inclined DG can use a raft of powers, such as power word stun, telekinese, use psychic powers, levitate, polymorph, throw up a Wall of Ice. And if he doesn't fancy getting his tentacles grubby, he can Gate in his Crew: demons galore, up to type VI beasties.
Despite being a part of Greyhawk, DG and most of his demon lord friends never appeared in adventures during my time in First. Along with Orcus he was one of the original demon lords developed for the game in Eldritch Wizardry in the 70s. Their rivalry set a tone throughout the incarnations and DnD editions of the Demon Lords. Orcus, to me, was all about that artefact wand which I recall using in an early campaign.
I never played 2nd to 4th, but as I understand the Demogorgon character evolved in depth, especially when Planescape hit in the 90s (for second, I assume). The 3rd edition had a campaign focused on his machinations, specifically the opposing plots of his two heads! What a cool concept, the ultimate split-personality demon. From there he featured in some big adventures (in Dragon magazine) wherein the players could actually have a dust-off with DG in the Abyss!
My brother has recently bought 5th, and I'm considering investing myself once I've played the classic set of modules with my kids (in order, U1-3, T1-4, S2, S4, A1-4, G1-3, D1-3, Q1.... and maybe WG6 for a giggle, to take them then through the Greyhawk Wars and then maybe some of those 2nd edition Vecna/ Rary ones). I hear that there's a campaign in 5th, Out of the Abyss, where DG pops up through a rift into the Underdark below the Forgotten Realms. As it's 1st to 15th level, I assume DG is still a bad-ass, and you get to try and fight with eyes closed against him the end. So perhaps my childhood love affair with a two headed mandrill dude isn't quite finished yet....