BX Monsters A to Z: Doppleganger

 The doppleganger, from the Basic Set, is up now for the A to Z treatment. (I'm going to use the official D&D spelling of the creature's name instead of the proper German spelling doppelgänger, even though spellcheck keeps underlining it in red.) Though I've rarely used them, dopplegangers have always been one of the more fascinating monsters to me. The Basic Set does well not to describe their natural form in detail, nor to offer a picture of it, keeping it suitably mysterious in my mind. In fact, the only bits I take issue with are the final sentence of the monster description and a single word from a languages table earlier in the book. More on that later.

The doppleganger is described as a man-sized, shape-changing creature that is intelligent and evil. It can take the form of any humanoid up to seven feet tall, and will attack that person. If possible, it tries to dispatch this target without the rest of the party knowing, so it can infiltrate the group and attack them later by surprise, usually when they're already dealing with another encounter. The Number Appearing is 1-6, both for the dungeon and wilderness, so it's possible multiple party members may be targeted at once.

Combat-wise, the doppleganger is a pretty tough foe for Basic-level characters. Its AC of 5 is solid and its 4 Hit Dice place it above any single Basic player character. Its single physical attack deals a formidable1-12 points of damage (making it one of the few things you really need a d12 for in Basic). I'm not sure why its movement is 90'(30') instead of the normal human base rate of 120'(40'). A morale score of 10 means it's a tenacious customer once it sets its sights on you and/or your party. Finally, it's immune to sleep and charm spells, and saves as a 10th-level fighter, making it quite resistant to any special attacks thrown at it. Its Morale score of 10 suggests that once engaged in combat, it's likely to fight to the bitter end, but there are other (and more appropriate) ways to interpret this, which I'll get to shortly.

And now we come to the bits that grind my gears: that last sentence of the monster description and the single word (the monster's name) in the list of languages.

*Warning*

*Expressions of strong personal preference ahead*

 "When killed, a doppleganger will turn back into its original form."

Not only does this refer to an original form that is never described, I don't believe anyone should EVER see a doppleganger's "true" form. The original doppelgänger of folklore is often described as a ghostly double. Not a flesh-and-blood double, but ghostly, as in spiritual or ethereal. The D&D doppleganger would go a long way toward maintaining its frightening aspect if its "true" form is a shadowy, vaguely humanoid figure with no features at all. If it is seen at all, it's almost always in poor light, and never more than a brief glimpse before it takes the form of its chosen victim. 

I also object to Doppleganger being explicitly listed as a language player characters can learn. Not only does this imply that dopplegangers have their own society and social order, it implies that humans can knowingly coexist with them long enough to learn it, which just takes the entire creepy mystique of the creatures and runs it through a wood chipper. Hey, not only do we know exactly what these things look like, but we can sit down for an afternoon chat with them too. NO!

Dopplegangers ought to be the stuff of ghost stories or dark faerie tales, not just another humanoid with special powers. Nobody knows exactly what they are or where they come from, or where they go when slain. Are they evil spirits? Malevolent fey beings? Creatures bleeding through from another reality? A person's own shadow self given material form? Nobody can say! They are NOT Mystique from X-Men, nor are they some magically engineered race of spies, or driven by simple human motivations such as greed for gold and gems (as ludicrously stated in the 2E Monster Manual).

Whatever a doppleganger actually is, though, once it chooses its target, as far as it is concerned or even knows, IT is the "real" character, and the other is an impostor, a rival who must be eliminated. Besides taking the other's physical form, the monster instantly knows all the factual details of his or her life. It is, however, not psychologically or emotionally human, and unable to comprehend its new memories in a human way. It will often display incongruous or bizarre reactions to normal situations. It is also, from the perspective of humans, evil and malicious, and finds pleasure in afflicting others with what we would consider to be cruelty and torment, either petty or severe. With knowledge of its victim's life and its own alien mind and spirit, it may display a twisted or inverted version of the original's personality. It may be aware of its difference from its ostensible fellows, and may conceal it as much as possible by avoiding social interaction or by affecting a distant or reserved demeanor when among company. Still, there should be something uncanny or "off" about them in a way that makes the original person's friends and associates uneasy -- an inappropriate facial expression, an off-putting gleam in the eye, a weird physical or verbal tic or mannerism.  

This doesn't mean it should be instantly obvious the character in question is a doppleganger. Unless the other party members explicitly state they are observing the replaced character, it may be a while before anything comes up organically in play to make them suspicious. (They are, after all, absorbed in a dangerous adventure.) The replaced character could also appear dazed, charmed, possessed, or simply keeping secrets. Magic may aid in detecting something amiss, but usually only when actively directed at the doppleganger, e.g. a detect evil spell, which probably still doesn't distinguish between dopplegangers, charms, and spiritual possession. 

So, how, in the context of a tabletop RPG session, does a doppleganger infiltrate a party? The best way is probably to attack an isolated character, such as an advance scout or a guard left alone. This works easily if the target is a low-level NPC hireling or retainer; you can probably just assume that a 4 HD monster easily overpowers the person. Or, if you want to drag things out, the NPC might manage to escape, and come racing back to the main party half-mad and gibbering incoherently about being attacked by himself or some such. Or the doppleganger itself could do that!

Replacing a PC is trickier, but can be done by conducting the relevant action out of the other PCs' sight in secret, either by taking the player in question to another room to play them out or by passing written notes (or, in this day and age, gaming out the whole thing via text message or the like.) 

For extra eerie fun, the doppleganger doesn't actually kill its victim (either it would have difficulty doing so, such as if the victim is its equal or more in combat, or it's led by its sense of malicious mischief to take some less lethal action). Instead it confines or incapacitates the victim, such as locking him in a room or closet, triggering a trap, or drawing a monster to block his way back to the party, and then itself returning to the party in the character's place, working some devilry against them for a while. It will eventually slip away before the jig is up, or flee when the original character escapes his predicament and turns up alive to expose the monster.

Alternatively, the doppleganger(s) could attack the chosen target(s) right in front of the party, counting on the other party members' inability to tell assailant from ally and so aid the ally. However, this would one way or another quickly reveal the doppleganger(s), as either the monster(s) are defeated and promptly dissipate, or they are victorious over the obvious corpses of their victims. Well, sometimes a monster must settle for a bit of quick mayhem rather than the long game of deception it would prefer. But it could also fight for a few rounds, and then flee, leaving the party shaken and unsure when or if, and in whose form, it might appear again... and it will, if given half a chance, if we interpret its high morale score as overall tenacity rather than simply courage or disregard for its own life in battle. Whether or not a doppleganger succeeds in killing its "impostor" in the dungeon, instead of continuing to harass the party, it could dash away to the character's home, taking the character's place in the community and causing no end of confusion and damage to the PC's reputation.

Assuming a doppleganger can infiltrate the party without being detected, it certainly could simply turn on them at their earliest inconvenience, or it could bedevil them in other ways for an extended period. Maybe it secretly disposes of some of their rations and equipment, or fails to warn them of traps or other hazards, or sneaks away to lead enemies to them. For a devious DM, a successful infiltration offers myriad possibilities beyond a blatant attack.

Aside from the overall flavor of the creature, the only things I'd change would be minor tweaks to its stats, such as making its movement match that of normal humans and dropping its morale, maybe to 6 or so, to reflect a sneaky, mysterious, alien nature rather than a combat-oriented foe.