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An accurate representation of the Brainslug larval stage.
I went down to the piercing parlor, said "please pierce my brain".
They said I won't survive it, so it had to be prepaid.

Brainslug is a mutation that gives +3 Brains and +25 stun resistance in exchange for -2 Brawn and -1 Reflexes, and several other downsides. It is one of the least popular mutations in the game, on account of its very specific advantages, punishing list of disadvantages, inconvenience, and general obscurity.


Brainslug's mutation is technically a spoiler, but like Empath, the mutation is so unpopular and the prerequisites so obscure that the wiki has long made an exception for its coverage. See the "Acquiring Brainslug" section for spoilers on this topic.


   Passive: +3 Brains
   Passive: +25 Stun resistance
   Passive: -2 Brawn
   Passive: -1 Reflexes
   Passive: Periodic money drain.
   Passive: Periodic stress when horny.
   Passive: Allergic to bleach.
   Passive: Cannot attack other Brainslug mutants
   Passive: Slugnet notifications


  • +3 Brains. This is a huge upside that opens the door to extreme Brains minmaxing, whether used for dedicated brains-max builds or combined with other potent mutations, such as Vampire. As an example, Brainslug mutants can feasibly pick VoxGuard Diamonds before they even drop N-tag.
  • +25 stun resistance. This is one of only two sources of flat stun resist in the game, paired with Hooligan (which Brainslug can synergize with). Just as with Hooligan, this is a very powerful advantage in combat.


Deathgear and Brainslug
Deathgear infects wearers with ATP, a disease which (at higher levels of progression), causes the infected to randomly attack targets on their tile. Unfortunately, as with Stench, the game considers the player's own mob as a viable target. While brainslugs will never properly queue attacks against themselves, much less cause harm, they will take substantial, periodic stress if heavily infected with ATP, especially if alone in a tile, because the game thinks that they are trying to cause harm to "one of slug".
  • -2 Brawn. Even for builds that dump brawn, this is a significant hit to carry capacity, and builds that do intend to use brawn will have to build around this.
  • -1 Reflexes. This is a hit to one of the most generally-important stats in the game. Fortunately, it's a pretty small negative, and depending on the build this is used with, it can end up being negligible.
  • Periodic money drain. Probably the biggest single reason that Brainslug is so unpopular, mutants have a random chance to lose anywhere between 1% to 5% of the credits in their wallet every heartbeat. This adds up fast, which means that brainslugs are essentially required to have corp deposit and corp withdraw permissions in their corp. Since this involves either trusting CEOs that can revoke your permissions and steal all of your money at any time or simply being a CEO yourself, most players find this very off-putting. Theoretically, it's also possible to paypal money to and fro from a friend, but this introduces even more problems than corp perms do.
  • Periodic stress when horny. This can be confusing at first. There is no flavor message to inform the player that something is amiss; they simply gain stress for no apparent reason, in large doses.
  • Allergic to bleach. Brainslugs cannot pick up any container that has bleach in it. Drinking bleach at any time (from a container on the ground) will permanently remove this mutation. The larval stage of Brainslug can also be used this way. This is an issue for freakslugs, who are thus unable to use bleach for maintaining quadruple implants.
  • Cannot attack other Brainslug mutants. In theory, this is almost always a non-problem, since brainslug is such a rare mutation, though there was once a humorous incident in a HellMOO PvP tournament where two Brainslugs were ineffectually paired together in a 1v1. In practice, this downside has a buggy interaction with deathgear.

Acquiring Brainslug

The only major prerequisites to this mutation are being able to bypass VoxGuard diamonds, whether the prospective Brainslug does this alone with en electromag inductor or with help of a picker friend, and the possession of at least one pair of mormon undergarments (found in Birchwood). Once these are secured, the following steps commence:

  1. Go to Weezer Sewers and find the Brainslug larva path, which is hidden in the southwest portion of the sewers (check lmap).
  2. Enter the larva chamber and open the organism storage. Chet will not attack on sight, and can be ignored.
  3. Immediately put the larva into a container. If allowed to linger in one's inventory, it will start to inflict debuffs.
  4. Go to the Radome in Star Field. Navigate to the first VoxGuard Platinum, and bypass it.
  5. Search the side rooms of this area until you find a post-it note. Ignore the mobs; they have been broken for years.
  6. Once the post-it is acquired, go all the way south in this area, and open the door with the combination on the note.
  7. Go all the way south to the stairwell, then go two floors down. Then, head north-west and locate the second VoxGuard Platinum. Bypass it.
  8. This small area contains two tiles; the southern tile contains the brainslug mutation, but much like Vampire, it is not possible to mutate Brainslug without full progression of the larva.
  9. Retrieve the larva from its container and hold it until it takes effect. Then, wait a few heartbeats until it reaches full progression. This is much faster than Vampire's infection; full infection takes about ten real-life minutes. Full progression will show a -3 debuff to Brains on @buffs.
  10. Walk south, and mutate.

Contrary to popular belief, infecting oneself before reaching the Radome site is completely unnecessary, and given the heavy debuffs that the larva imposes (which include spawning mentals, tripling hunger rate, and imposing -3 Brains), also unwise.


Brainslug has the dubious accolade of being the most heavily-nerfed mutation in the entire game. It used to come with a slew of interesting perks involving slugnet, infectious larvae, the ability to see other slugs' locations on slugnet, and even the ability to control NPCs, which made the trade-offs much fairer. All of this was removed many years ago, on account of its abuse potential. Attempting to use slugnet will still return a message, declaring that it has been "temporarily" disabled due to abuse. In truth, no admins have expressed interest in restoring brainslug at all, and some have expressed interest in simply removing it. In all likelihood, Brainslug will remain as it is indefinitely.


This mutation adds the following line to a character's description:

   An unnatural lump protrudes from the side of his/her head.

Racial Mutations AbominationChromemouthChudEmpathGenetic PurityHideous FreakVampireZombie
Focus Mutations CarrieChillerFuck MachineSalamanderScreechWrithing Smoke
Movement Mutations LeapfrogPhaserClairvoyance
Soak Mutations High DensityFirewalkerRubberskinSnakeskinYeti Skin
LithodermisSolar SpongeSilicone SkinEelskinYeti Fur
Miscellaneous Mutations BillygoatBleederBloodhoundBrainslugBrute StrengthCamelfatEnigmaFibrocartilageHooliganHyperimmuneIron LiverJunkratMuleNimble FingersPlant WhispererRipperStenchTwitchy NervesSuperclotXray Vision
Joke Mutations Cat Ears • Caucasian • Third Nipple
Defunct Mutations Jammer