Best Monsters To Use For A Mystery Campaign In DND

Summary

• Intellect Devourers offer unique abilities for mystery campaigns, creating intrigue and suspense.
• Animated Objects fit well into mystery settings, adding surprise and fun to encounters.
• Beholders make for intense boss battles in high-level mystery campaigns, posing a significant challenge.

Mystery campaigns or arcs can add a fun new flavor of fantasy to any long-standing Dungeons & Dragons table. Whether your party is investigating a murder most foul, or unraveling the schemes of an ancient crime syndicate, mystery-themed adventures prove fun for the whole party.

But, if you’re running a mystery campaign for the first time, you might be wondering how to build combat encounters, or even construct a random encounter table. That’s why we’ve created this list, which features a host of monsters you can use in your mystery campaign to create atmosphere, tone, and intrigue. Here are the best monsters for a mystery campaign.

10

Intellect Devourer

Though Intellect Devourers are ultimately a low-level monster to contend with, their Steal Body and Devour Intellect abilities are not to be trifled with, and can prove formidable for underpowered parties. These creatures can essentially attach themselves as hosts to weakened targets, controlling them for a period of time.

This can make for a great reveal in a mystery campaign. If players are wondering why familiar NPCs are acting differently, they might want to consider if they’ve come under the influence of an Intellect Devourer.

9

Animated Objects

Animated Objects prove to be a fun, if not slightly easy encounter for low-level parties to contend with. What makes these objects, which can range from animated brooms to animated suits of armor, fun for mystery campaigns is that they fit right into the typical locales you see in intrigue-based adventures.

If the party is exploring a decrepit manor, or perhaps even an underground lair, Animated Objects fit right in with these types of settings. Plus, they make for a fun reveal when springing to life for the first time, potentially triggering the Surprised condition in combat.

8

Assassin

For mid-level adventuring parties, consider using an Assassin as a formidable, stealthy opponent for the table to contend with. Obviously, Assassins make for great atmosphere when it comes to mystery campaigns, particularly if you want to incorporate a murder element to your adventure.

For all intents and purposes, Assassins essentially function like low-level rogues, which can be a bit boring. However, you can homebrew this stat block to include things like poison attacks, sleep darts, and more to make them more of a challenge.

7

Beholder

For higher-level adventuring parties, consider using a Beholder as a climactic boss battle that wraps up a mystery campaign. As these creatures are highly dangerous and also incredibly smart, they make for perfect antagonists in mystery adventures, and can be fun to reveal at the end of a long arc.

Just be careful when using Beholders as they have many abilities that can essentially wipe mid-level parties off the map in seconds. Make sure your party is appropriately balanced to take on such a foe before throwing them into a TPK.

6

Cloakers

Cloakers make for great monsters in mystery adventures due to their deceptive nature. Though typically found in the Underdark, there’s no reason why you couldn’t incorporate a Cloaker into an urban setting as well. Before combat, Cloakers tend to look like hanging robes or cloaks, meaning they can surprise and frighten players.

The best part about Cloakers is they can attach themselves to creatures during combat, blinding them. This is sure to strike fear and suspense into the hearts of your players, creating a fantastic atmosphere for your table.

5

Cultists

It’s almost a cliché at this point, but so many mystery stories, and even horror campaigns, end with the reveal of a cult. But, just because it’s played out, doesn’t mean it’s also not tried and true. Cults make for great antagonists in mystery campaigns, and can work for all manner of party compositions.

Your campaign can easily culminate with a climactic battle between players and the nefarious cult that’s been lurking in the shadows the whole time. For extra fun, consider revealing that a key NPC from your mystery campaign has been a part of the fanatic cult the entire time.

4

Doppelganger

True to form, Doppelgangers can shape-shift, resembling any humanoid they see fit. This, of course, makes for great story fodder in a mystery campaign. Revealing that Doppelgangers are in the party’s midst means they’ll think twice before trusting any NPCs they come across.

Additionally, Doppelgangers can read thoughts as if they’re using the Detect Thoughts spell. This makes them dastardly opponents to go up against both in combat scenarios and roleplay situations. The 2025 Monster Manual also has a table you can roll on to determine what the Doppelganger’s schemes are if you need inspiration for your campaign.

3

Mages

Every great mystery campaign needs a great puppet master pulling the strings behind the scenes. Mages of all varieties make for great candidates for this role. You can also have a lot of fun tweaking the alignment of mages to suit your needs. Perhaps a Neutral mage thinks that their plot is actually for the good of all, despite what the suffering populace thinks.

Mages are great as you can also tailor them to your party’s needs. If you’re DM-ing for a more high-level, seasoned group of adventurers, use an Archmage to really keep them on their toes.

2

Mimic

Mimics are one of the most classic Dungeons & Dragons monsters that have found their way into nearly every edition of the game. If you’re a veteran player who hasn’t fought a mimic, you’re in the minority. Mimics are disguised objects that can resemble things ranging from treasure chests to topiaries, depending on the location they’re in.

These make for great encounters in mystery campaigns, as using one Mimic will keep your players suspicious of all treasure and objects they find going forward. After all, who knows if that’s a real sword or just a Mimic waiting for something to snack on.

1

Rakshasa

When it comes to devious plots and machinations, there’s no better monster than the Rakshasa to serve as your mystery campaign’s primary antagonist. Rakshasas are fiends that often thirst for revenge, and resemble humanoid-like tigers with backwards palms.

Make sure you only use these creatures for high-level parties, as they have access to a wide host of abilities from innate spellcasting, Magic Resistance, multiattack, and more. Plus, when they’re killed outside of the Nine Hells, they return to the Hells, fully restored. For a Rakshasa to go away for good, they must be defeated in the Hells.