In the Original Edition, it was not anathema to consider doing something "gonzo" like playing a Balrog or some other monster (I believe there was a vampire character in Arneson's campaign, which brought about the cleric class as a counter-force to undead). However, in the First Edition Dungeon Master's Guide, Gygax (presumably) made the point to frown upon using monsters as player characters, offering various "gaming" and, for want of a better word, psychological reasons why this should not be so.
This got me to thinking about why it was allowed in OD&D, but not in AD&D. Gygax goes to great lengths to explain why a monster as a PC does not work in AD&D, and yet it was an option, subject as always to the whim of the Referee, in OD&D. Reading through the relevant section in the DMG gives one the impression that its all about a humanocentric campaign, and so on.
However, I wonder if there is a more fundamental reason why this notion was looked down upon in the later edition. OD&D, of course, had its roots in Chain Mail and the wargaming background of both Gygax and Arneson. Indeed, all of the LBBs and the Supplements have as their subtitle, "Rules for Fantastic Medieval Wargames Campaigns Playable with Paper and Pencil and Miniature Figures."
Now, folks can (and have) argued that OD&D was really a new thing, that it was no longer a wargame, that it was now a ROLE PLAYING game, and so on. That all well and good, but is not the main point here. Lets suffice to say that OD&D grew out of wargaming, and that even if it shouldn't be considered a wargame in the "true" sense of that term, it was in fact heavily influenced by wargaming and shows a great amount of similarity to them in many ways.
One of the (many) criticisms of AD&D is that it grew away from its roots. Now that is not to necessarily say that this criticism laments that AD&D grew away from its wargaming roots (although this is one such criticism); usually such criticisms revolve around the game becoming too complex, too rules heavy rather than "rules lite," that the game moved away from its "dungeon" roots, the power curve went way up, the DM became straddled with rules (and rules lawyers) rather than living in that OD&D "sweet spot" some refer to as "rulings, not rules," that the game became more dogmatic about the right way to play in contrast to the "fast and loose" feel of the Original; and so on, ad infinitum.
However, if we harken back to the roots of the game, to wit, the wargame, we may come to a much simpler reason why the monster as PC was no longer acceptable, and it may shine some light on why the paradigm shifted from the Original edition to the next Advanced edition. Namely, it is the fact that the game had shifted from its wargaming roots to "something else," as illustrated by the fact that the player no longer controlled a gaming piece (i.e., a miniature figure), but a character. In other words, the player no longer controlled the pawn on the chessboard, or the shoe on the Monopoly board, but something else, something different, something that was meant to be role played, rather than simply "roll played" and pushed around the game board.
The Balrog, or vampire, or whatever, was much more acceptable to the Original gamer than the Advanced gamer, because the Balrog was closer to being a gaming piece, a token, than he was a character.
On a fantasy wargaming battlefield based on Chain Mail, it might be totally common to see a player field a force of orcs, trolls, and ogres as soldiers, with some special units like a dragon, a manticore, or perhaps a Balrog, all led by an evil wizard, with the opposing team made up of true men, elves, dwarves, hobbits, perhaps with a flight or two of giant eagles or hippogriffs, and backed up by their own powerful wizard or cleric. These units were basically nothing more than metal figures or paper chits assigned variable numbers with which to simulate a combat.
With the LBBs, the battlefield had shrunk from unit action to "man-to-man" action, and had indeed moved off the battlefield and down into the dungeon. The miniature figure no longer represented a unit of men, or a "special unit" that was a cog in the greater war machine, but was instead a hero, an individual piece; a nascent persona. He was now something much more closely tied to the player. No longer was the player constrained to merely overseeing the action, to act as general of his miniature army; he could now be the piece, in an imaginative sense, and live out his fantasy.
This is the much more important paradigm shift between the Original and the Advanced to my mind. The Original game still wasn't sure what it was supposed to be, existing in the older, wargaming paradigm, while at the same time it was becoming, or embracing, the new role playing paradigm. The Advanced game thought it knew what it was (whether it achieved that or not is beside the point), and it certainly was no longer a wargame.
Certainly the Advanced game had most, or at least many, of the trappings of the wargame. There were detailed rules for man-to-man combat, aerial combat, naval battles, hiring non-human troops, advancing to name level and becoming a lord, building a keep or other stronghold, etc. However, the action now was the player, or at least the party, against the world.
Perhaps this is where some dissatisfaction or frustration comes from when high level play is reached. Its been said that at high levels, the game begins to break down, as the characters are simply too powerful, have too many magic items and spells, and the overworked Referee must resort to throwing larger numbers of foes against them. With a +5 to this and a +3 to that, the numbers become so great that dice rolls almost become meaningless, and the winner is often the one who was able to strike first (and thus last!).
High level characters may be the shoals against which many campaigns founder, because they have not moved on to their natural, logical conclusion; namely, the battlefield. When all of the other challenges in the game are no longer challenging, perhaps its the battlefield where higher level characters belong, commanding vast armies and shattering enemy kingdoms. The term campaign itself made a paradigm shift between the wargaming days and the roleplaying phenomena, where a campaign in the former meant war upon the battlefield, and a campaign in the latter meant episodic adventures in the gaming milieu.
Maybe this illumines as to the a reason that most high level campaign fall apart, why most groups prefer to reboot to new or lower level characters rather than advance to the next level, the fantasy wargame. Role players are used to being the individual piece, having an attachment to that character sheet, not wanting it to be nothing more than an "advanced gaming piece," as some have quipped. To assume the role of king, or baron, of lord, to marshal one's forces and set off against the enemy in battle, to rule a kingdom and all that goes with it (even in a fictional game kingdom) moves that persona back onto the game board, at least to some degree, and forces the player to a level of detachment that may not be comfortable.
After all, most of us enjoy adventure gaming, and didn't Conan himself lament his days as king, dealing with the court and the business of ruling and governing, longing instead for the days of high adventure?
“...these matters of statecraft weary me as all the fighting I have done never did. I wish I might ride..." said Conan. “It seems ages since I had a horse between my knees. When I overthrew the old dynasty... it was easy enough, though it seemed bitter hard at the time. Looking back now over the wild path I followed, all those days of toil, intrigue, slaughter and tribulation seem like a dream."
“I did not dream far enough... When King Numedides lay dead at my feet and I tore the crown from his gory head and set it on my own, I had reached the ultimate border of my dreams. I had prepared myself to take the crown, not to hold it. In the old free days all I wanted was a sharp sword and a straight path to my enemies. Now no paths are straight and my sword is useless." -Robert E. Howard, The Phoenix on the Sword.
When I was a fighting-man, the kettle-drums they beat,
The people scattered gold-dust before my horse’s feet;
But now I am a great king, the people hound my track
With poison in my wine-cup, and daggers at my back.
– The Road of Kings.
If we were to move our high level campaigns from man-to-man scale to wargaming scale, perhaps we'd lose that sense of identity with our characters, that sense of persona, and for want of a better term, that sense of closeness. But maybe that would be a good thing. Maybe we need a little detachment.
This begs the question; does the wargame offer adventure, enough to sate whatever it is we crave when we role play? Might it offer new vistas to a campaign that has become stale, even though it may require us to accept a level of detachment from our "advanced game piece?"
I dare say it might.
“Know, oh prince, that between the years when the oceans drank Atlantis and the gleaming cities, and the years of the rise of the Sons of Aryas, there was an Age undreamed of, when shining kingdoms lay spread across the world like blue mantles beneath the stars... Hither came Conan (the adventurer), the Cimmerian, black-haired, sullen-eyed, sword in hand, a thief, a reaver, a slayer, with gigantic melancholies and gigantic mirth, to tread the jeweled thrones of the Earth under his sandalled feet.” – The Nemedian Chronicles.
Let our campaigns become such in the truest sense, the older sense, that we might get over ourselves and let go of that stained, dog-eared "advanced game piece" of paper, realize what the accumulation of riches and minions is for, and grasp that most fleeting of prizes....