I have talked a lot about demons this month and about Hell prior to this. The one thing I have not talked much about is the Big D himself, The Devil aka Satan.
Here are two things you likely didn't know about Satan in RPGS and D&D in particular.
First, he usually doesn't appear in them. In fact there are no official stats for Satan/Lucifer in D&D in any edition. Plenty of stats in third party products, but none for the guy himself.
Secondly, I never use Satan in my games. Not because I don't want too or have any fear of it, simply put there is no way he could ever live up to expectation of the players.
One lucky roll and all my carefully laid plans become, oh hey we just killed the Source of All Evil. How many XP do we get? There is just no way that stats on paper can match up with the expectations of the players. With a character like Dracula it is easier. He can be just as evil, just as much of a threat to the characters, but we know something else about Dracula. It's the same as Smaug, or Voldermort, or Vader or Sauron. These evils can and were defeated. Satan is, or at least should be, an unstoppable dreadnaught of evil. He is not the Monster of the Week, he is not even the Big Bad. He is the Biggest Bad EVER.
Despite the lurid tales from the 80's (check out Asshat Paladin's review of "Playing with Fire") or Pat Robertson's claims, D&D players are not Satanists. Sure, maybe some are. But no more or no less than say the general population (which is much smaller than people generally think).
Lucifer as Satan has appeared in the pages of Dragon Magazine and in the various Tome of Horrors books.
Satan made his appearance in Dragon #28 from 1979 in the infamous Politics of Hell article. Here are the stats he had then:
FREQUENCY Very rare
NO. APPEARING 1
ARMOR CLASS -8
MOVE Whatever desired
HIT DICE 333 hit points
% IN LAIR 5%
TREASURE TYPE H(*2), l(*2), U(*2)
NO. ATTACKS 1
SPECIAL ATTACKS +3 or better weapon and purity of heart required to hit
MAGIC RESISTANCE 95%
ALIGNMENT Lawful evil
PSIONIC ABILITY Special
Attack/Defense Modes Special
and his more recent S&W stats:
(Satan from the Tome of Horrors Complete, Copyright 2011, Necromancer Games, Inc., published and distributed by Frog God Games; Authors Scott Greene.)
Hit Dice: 25 (150 hp)
Armor Class: -6 
Attack: Rod of Infernus (3d6), bite (2d4 plus poison) or 2 claws (2d8), bite (2d4 plus poison), tail sting 1d8 plus poison)
Saving Throw: 3
Special: Gaze weapons, spells, summon devils, +3 or better weapon to hit, immunity to fire and poison, regeneration (4 hp/round), magic resistance (90%), see in darkness, telepathy 100 ft.
Move: 21/30 (flying)
Challenge Level/XP: 40/10400
The Pathfinder stats are even more powerful.
EVEN then there is some character out there that could take this guy. Maybe not many, but they are out there.
Lucifer and Satan have appeared as seperate entities in the old Death's Edge Games Inferno games.
Which got me thinking, what if "Satan" isn't a person, but a title. Not "Satan" but "the Satan", similar to what I did for Demongorgon. The idea is not really an original one, Piers Anthony covered it in his Incarnations of Immortality series and it was covered well in the Charmed series with their Source of All Evil concept.
So the idea here is take a demon, already powerful, and juice him up on all the power of evil, or Evil, and he becomes the ruler of all demons. Take a page from Lexx and His Divine Shadow and make it so that the new host of this evil power, the new Satan, has all the memories of all the previous Satans AND the knowledge of the new host. That is a very dangerous foe.
So lets combine this idea with Dante's Inferno and some from the the D&D game itself. In D&D there is a god of Evil, Tharizdun (who I'll talk about more tomorrow) that is roughly the same as Lucifer/Satan.
Tharizdun is trapped in a prison where his jailer was Asmodeus. Asmodeus is now the leader of Hell and Tharisdun is forgotten. There are a lot of clues to his whereabouts and even Gygax himself featured him in his Gord the Rogue books. So my solution is to split "Satan" up into a couple of beings. Part of him is the imprisoned Beast and another part in actually part of Asmoeus.
Another part...well I have not figured that one out yet.
The real question that in a world FULL of demons, devils and all sorts of monsters what purpose does Satan serve? What does he do?
The recent Kelley Armstrong book "Thirteen" finally features Lucifer. He is very different than what is typically expected. Two of my favorite versions was Peter Cook's in Bedazzled and Viggo Mortensen in The Prophecy for different reasons. Maybe I should do that for my next October Movie marathon, only watch movies that feature the Devil/Satan as a character.
I also have something to say about RPGs and their role in the Satanic Panic of the 80s. But that needs to be for another day.