Resistance is futile. You will be assimilated.

[Hriston]

In Star Wars: The Clone Wars, Season 2, Episode 7 "Legacy of Terror" and Episode 8 "Brain Invaders", the Geonosians are part of a hive mind controlled by their queen, which is spread by brain worms. You could probably do something similar with Giant Ants. Or even better, Thri Kreen are described as having a hive mentality, and a particular subrace, the zik-chil, physically modifies themselves and other species. That seems to fit the bill.

 

[Shadowdweller00]

So, let's say I wanted to include a race in my campaign that are, thematically, the D&D-equivalent to the Borg from Star Trek.

Let me stress "thematically." I'm not looking to create D&D cyborgs or anything that necessarily physically resembles the Borg. The important factors I'm looking to import are:

1) Hive mind/lack of individuality, and

2) The existential threat of being converted/absorbed into the hive, losing who you are and becoming the enemy.

And I don't want to go with undead.

Now, with those factors in mind, what already existing monster or race would you recommend I use? (Bonus points if it already exists in 5E, but something from any edition will do. I don't want to homebrew something brand new for this, for various reasons.)

I'm willing to make a few minor changes/tweaks to the monster, but nothing that transforms them so completely that they're not recognizable.

I'd suggest Formians

 

[jasper]

So, let's say I wanted to include a race in my campaign that are, thematically, the D&D-equivalent to the Borg from Star Trek.

Let me stress "thematically." I'm not looking to create D&D cyborgs or anything that necessarily physically resembles the Borg. The important factors I'm looking to import are:

1) Hive mind/lack of individuality, and

2) The existential threat of being converted/absorbed into the hive, losing who you are and becoming the enemy.

And I don't want to go with undead.

Now, with those factors in mind, what already existing monster or race would you recommend I use? (Bonus points if it already exists in 5E, but something from any edition will do. I don't want to homebrew something brand new for this, for various reasons.)

I'm willing to make a few minor changes/tweaks to the monster, but nothing that transforms them so completely that they're not recognizable.

So evil elves.

 

[Gardens & Goblins]

A mundane yet well orchestrated religion/cult could have the same effect. Or a clique or other exclusive group - think 'Secret Society' - with the right kind of setup. It'd also be so much harder folks to counter directly with force.

For example,When rumours of the End o' the World are spreading, and a secretive yet powerful, charismatic figure/group appears offering salvation, how many folks will follow - and what will they do to gain favour?

Add in a magical twist -- perhaps the secrets they offer shatter the mind -Lovecraftian insight into reality. Secrecy and power. How many 'Faithful' are in the tavern? Who else knows? Why are the villagers all gathering outside...?

 

[Savage Wombat]

I have this exact scenario in the list of sandbox locations for my new campaign warming up. Although, if anyone comes up with any further development of the idea, I'd love to hear (steal) it.

 

[jaelis]

Modrons is really good, but how about koa toa, with aboleths as sort of queen bees? Converting a humanoid to a modron-like form seems like a stretch, but letting an aboleth turn them into a koa toa seems more believable.

 

[Eltab]

The closest thing I can think of from the published APs would be the Myconids. I thought their chapter from Out of the Abyss was just creepy.

Copy from Princes of the Apocalypse: have a doom-prophet who is secretly responsible for the bad / scary portents &c that the un-knowledge-able leaders turn to him for interpretation.
This is how the PCs are first introduced to the problem. The doom-prophet was a 'failed assimilation' who now works for the hive-mind's goals without being part of it.

 

[Paul Farquhar]

The I Robot scenario would work well with Modrons. Maybe the ruler of the Kingdom made a warlock type pact (a use for Celestial patron?) with a high ranking Modron and instructed them to eliminate all conflict and suffering in the kingdom?

 

[Jacob Lewis]

The Spell plague from 4th Edition FR inflicted spellscars on everything it infected. I believe Neverwinter Campaign Setting featured a monastary specializing in treating infected beings, but was actually run by a demon or devil who converted the sick into a spell-infused army for her own agendas. Good stuff. (That book was one of the best products to come out of any edition.)

 

[Dannyalcatraz]

Aboleths can create thrills, right?