Using the Doppelganger

 When I've thought about the possibility of running a campaign set in Ravenloft, I've honestly kind of struggled to come up with my own original Domains, even with the guidance given in Van Richten's Guide to Ravenloft. The issue there is that I think my mind starts with the aesthetics of a domain, and the guidance (probably correctly) starts instead with thematic concerns. For example, I like the aesthetic of a sea-soaked harbor town out of a Lovecraft story (perhaps without the underlying racism) and think some cosmic horror elements would work really well in such a setting, but in a way, I'm sort of putting the cart before the horse. Domains of Dread are built around Darklords, and are reflections of them.

I did have some vague ideas for a domain-hopping Ravenloft campaign/adventure, which started with a particular motif: the Doppelganger.

Doppelgangers are fitting tropes for Gothic Horror, which are all about the potential for evil and monstrousness lurking within the human mind. While not monstrous in the same physical way as a vampire or werewolf, a Doppelganger raises questions about one's own identity and what other paths we might take. It can also veer into a kind of Cosmic Horror - one of the core elements of our own identities is that we are unique individuals. But if we were faced with our exact double, might we begin to question just how unique we really are?

As a trope, the Doppelganger almost certainly predates the German word we use for it, but in English parlance, rather than the specific D&D monster, a Doppelganger is just someone's double (I think the German word literally means "double-walker"). Naturally, given how many human beings there are, and the fact that we're all actually very similar genetically, it's natural that some people coincidentally happen to look like one another.

But we're also deeply keyed into distinguishing between human faces. Even, say, a pair of brothers that look very much alike will be trivial to distinguish for those who are familiar with them.

I think there's probably some kind of weird wire-crossing when we encounter someone who looks similar enough to someone else that we genuinely mistake them for the person. It's an uncanny moment, especially when we start to realize that it's not the person we thought it was, and all of the distinctions in their appearance are taken not as what they are - which is just the normal distinguishing features - and more something being just kind of wrong.

Humans are social animals, and social bonds rely on familiarity and trust. When I come home and see my roommates, their familiar appearance is a reassurance that I know who they are, and can expect that their behavior will continue to be safe and friendly to me.

And that's what makes Doppelgangers, the monsters, so potentially unsettling.

Here's the thing: D&D is a game built originally around delving into dark and dangerous dungeons, where you might find a bunch of zombies or a golem or a demon in some room.

I don't think you should ever waste Doppelgangers as dungeon fodder. Statistically, they don't really do much interesting in combat.

Instead, we need to build the use of these creatures from the ground up to make a reveal particularly interesting.

As we said before, social bonds rely on familiarity and trust. The Doppelganger monster is built to simulate that. Naturally, its most notable feature is that it's a shape-shifter, but it goes farther than that: it can also cast Detect Thoughts without any spell components (meaning that you won't know they're casting a spell unless you're reading their thoughts - or perhaps using something like Detect Magic while observing them). Even if they push deeper into your minds and you realize you're being read, the lack of spell components means that you might not know that it's actually them doing it.

The function, of course, of this Detect Thoughts ability (or Read Thoughts, which is the ability that lets them cast the spell this way) is that they can potentially fool someone even if they use common-sense techniques to foil an imposter: the old "get them to reminisce about something in the past that never happened" trick won't work if they can tell that you're thinking about the fact that it's a false story.

Now, Doppelgangers are not inherently evil, and are given the Neutral alignment in the new MM (which also serves as the "any alignment" tag). Still, it's very easy to imagine them as terrifying monsters. They are not humanoids, but monstrosities (interestingly, the "playable version," the Changeling, is now considered Fey) and while that doesn't rule them out being relatable characters (Thri-kreen, who are now consistently classified as monstrosities, are also a playable species) it also gives you, as DM, license to make them deeply strange and alien. Indeed, their natural appearance as illustrated in the 2025 Monster Manual is very much "alien," as in the sort of "Greys" trope, lacking even a nose and mouth, so that they look like they could come out of a flying saucer and pull an Invasion of the Body Snatchers kind of plot.

I do think that the kind of campaign you'd want to use this in would be one that involves familiarity. A lot of the campaigns I've played in have been a bit more about traversing a wide world, moving on from location to location without really returning anywhere. A campaign of this sort can still use Doppelgangers, but I think if you really want to get your bang for your buck, a campaign in which the party forms relationships with recurring NPCs who can then be replaced by them is going to probably be more effective.

Doppelgangers have proficiency in Insight and expertise in Deception, and with their Read Thoughts, they can generally pick up enough of their impersonation target's overall vibe to make a convincing double. But at only CR 3, that means those bonuses are not going to fool every player character who doesn't have expertise in Insight.

And here, I think, largely giving advice to myself, I should point out that a Doppelganger's discovery is the fun moment for these monsters. When their deceptions are found out, that's when the shit hits the fan, and we get an exciting encounter - even a combat encounter, in which the Doppelanger is likely to try to just get away and hide. If they're there specifically to kill a PC, they'll do whatever they can to avoid detection until the character can be isolated.

In terms of balancing such an encounter, I'd say you want it to feel harrowing - it should be a bit too difficult for a single character to take on a Doppelganger (otherwise why would they be the one sent to take you down?) The character would have to get back to their party to feel safe, and that's when you either have the Doppelganger slink off into the crowds and let them go - leaving them a constant paranoid threat for the party - or, if you want to fully pop off, you have a whole bunch of Doppelgangers working together to spring on the party at the same time.

I do think, though, that the entire monster is built around the dawning realization that the person you're talking to is not the person you think they are. The most flagrant way you could do this is by having a character discover the real person's dead body, but another likely scenario based on game mechanics is just if the PC succeeds on their saving throw against Detect Thoughts. Even if, as we said, there's no obvious indication that the Doppelganger cast the spell, your player is going to be on the lookout once they're asked to make a Wisdom saving throw (though remember that if the Doppelganger doesn't delve deep and only gets surface details - a distinction that isn't super-clearly defined - there's no saving throw to make).

I would say, as a DM, to couch the language about the saving throw in a way that doesn't make it to obvious - "you get this strange spike of paranoia, feeling as if someone is watching you."

It is tough, of course, to avoid metagaming when you fail a saving throw against something like this or like Scrying, so you might also want a clever Doppelganger to set themselves up in a situation where there is plausible deniability - maybe they probe someone's thoughts when the target is speaking with someone else, making the PC suspect the person they're currently talking to and not the random bar patron ten feet away.

Still, again, remember that these monsters become fun when the jig is up - and really savor that moment. You want to go through different steps - first, the general sense of offness, then describe the disguised Doppelganger's previous methods of seeming likable and trustworthy now laid bare as a malevolent artifice, the too-broad smile, the unblinking eye contact. It's that moment where now the PC knows something that the Doppelganger doesn't - which is that they know they're a Doppelganger (or at least know that they're not who they say they are.) And now, the tension becomes whether the PC can play it as if they don't yet know, and if the Doppelganger clocks that they've been made.

What will they do? Will they try to kill the PC to maintain their ruse? Will they dart and hide to take on a new identity so they can continue whatever plot they were in the middle of?

Even when the monster is defeated, the very existence of such a creature should leave players with a lingering sense of paranoia. Ideally, long after you're done using them as monsters (and with only a single CR 3 stat block, you're probably not going to be using them throughout a campaign - I'd have loved to get a CR 7 or 8 "Doppelganger Assassin" stat block) the party will feel a bit uneasy with everyone they meet.