Metalhorror

The Metalhorror is an entity that can threaten your colony. It will infect your colonists one by one and burst out of them when it is ready to attack.

Occurrence

A Metalhorror infection generally begins as a hidden illness suffered by a single pawn, which is initiated by a storyteller event that targets a pawn with a valid infection pathway. Creepjoiners often come with drawbacks- one of which can be a metalhorror infection. Pre-infected pawns may arrive as guests or raiders.

During the monolith awakening, several mature metalhorrors will be spawned to defend each void structure. Additionally, once all void structures are defeated, a final group of metalhorrors will spawn around the void monolith.

Infection

Metalhorrors are entities that infect humans through their hosts, creating more of themselves as they do. It is possible to test or interrogate pawns in order to find out who is hosting a Metalhorror. Upon detection through surgical inspection, and a random chance from being detected by interrogation or going undetected for too long, All Metalhorrors will emerge out of their hosts and inflicting cuts. The death of any host will also cause them to emerge, even if they have not been detected first. When emerging, metalhorrors will deal enough damage to down most hosts:

They will never leave scars or kill their host when emerging
Ghouls and painless pawns can still be downed through damage to their legs. If they are not downed, they will have received enough damage to nearly kill them.
Unconscious and incapacitated pawns will still receive damage albeit to a lesser extent.

Metalhorrors can spread between colonists in various ways and cannot be detected before a gray flesh sample has been found.

The initial infection is activated by a miscellaneous storyteller event that chooses a random pawn with a valid infection pathway:

Implantation before arrival. This applies to any pawn upon first spawning, except for your initial colonists and babies. This will be listed as "implanter insectoid" for creepjoiners despite insectoids not being a valid infection pathway.
During revenant hypnosis
The melee attack of a shambler, fleshbeast, noctol, or sightstealer.

Metalhorror implantation events do not cause any letter to appear however gray flash appearing does.

Note that an infection pathway is not by any means guaranteed to become a full-fledged metalhorror infection. Pawns with infection pathways are not considered metalhorror hosts and will not spread the infection or generate gray flesh until and unless the metalhorror event triggers on them. An infection pathway expires after 30 days. If a metalhorror event triggers when no player controlled pawn possesses a valid infection pathway, the game will spawn a creepy joiner with a hidden metalhorror infection. It's highly recommended for players to quarantine new creepjoiners until they have been cleared for hidden infections. This is especially true if the creepy joiner spawned immediately after conducting a void provocation ritual.

Once a metalhorror infection is active, its host can secretly spread it to other pawns. Pawns infected this way gain the metalhorror infection immediately, rather than using the infection pathway system, and as such can start infecting other pawns from the moment they're infected. The following activities, when performed by an infectee, can spread a metalhorror infection:

Infection event	Details	Infection chance per event
Sharing a bed	An infected pawn sharing any two-person bed or sleeping spot spreads the infection to any bedmates. The pawns do not need to be in a relationship or participate in lovin for the implantation to occur. Pawns sharing the same barracks but not the same two-person beds or sleeping spots will not spread the infection.	100%
Performing surgery	Any medical bill performed on a pawn by an infected pawn can spread the infection This includes minor operations that might not be obvious as vectors, such as anesthetization, administration of drugs, xenogerm implantation, and blood transfusions. Tending does not spread metalhorror infections.	50%
Cooking a meal	Each meal cooked by an infected pawn has a chance to infect a pawn that eats it. This chance is rolled upon consumption, not upon creation of the meal. It is not known whether this shares the stack probability splitting of food poisoning when placed in a stack.^{[Detail needed]} Pemmican is unaffected by this. After the infection is revealed, it is possible to have your colony reinfected by tainted meals.^{[Detail needed]}	4%
Unnatural healing	Use of the ability by an infected pawn on an uninfected pawn spreads the infection	100%
Feeding patients	AN infected pawn feeding anything to a patient can infect the patient. This includes hemogen packs being fed to hemogenic prisoners and patients.	30%

Detailed Information to be cleaned up

There are two separate MetalHorror incidents. Both fire as Minor Threats.

MetalHorror Implantation fires on a random colonist that meets specific criteria such as recently joined colony or damaged by anomaly entities. Requires monolith level 1. Earliest day 30, can refire after 45 days, requires a colonist count of 4 and 300 Raid Points.

Creepy Joiner infected with metalhorrors: Requires monolith level 2, earlist day 10, and can refire every 60 days. Does not have a raid point nor colonist count requirement.

The first grey flesh appears 1.5 to 2.5 days after infection. When a gray flesh is to be dropped, there is an additional 1 to 12 hour delay. One gray flesh can drop every 3 to 10 days.

If half of your colonists are infected, the chance for metalhorrors to emerge will approach 100% after a few hours.

Summary

Contrary to other non-humanlike entities, they have three different life stages. They need 1 day to grow from larva to juvenile, and another two days to grow from a juvenile to a mature metalhorror.^{[Counts time inside?]}

Metalhorrors do not leave behind corpses when killed, instead breaking down into a pile of 10-20 bioferrite, and occasionally 1 shard.^[Chance?]

Containment

The metalhorror yields 3.2 to 4.4 bioferrite and 160W to 220W per day.

Combat

When attacked, metalhorrors only receive 25% of damage. They can be stunned by EMP, but never adapt to it. They also have 200% flammability.

A metalhorror's attacks are identical to those of a scyther. Metalhorrors attack with a blade attached to each arm, dealing a massive 20 damage per blade. While they technically have a blunt Head attack, they will never use it unless their arms are destroyed. Even for brawlers with high melee skill, metalhorrors are extremely dangerous.^[Maturity?]

Metalhorrors' legs have a total of 36% chance to be targeted by damage, almost twice that of humans. This makes them more likely to have both legs destroyed in combat.

Melee Attacks	Damage Amount	Cooldown
Cut	20	2.0 sec

Metalhorrors have a psychic sensitivity of 150%, making certain psycasts more effective on them.

Analysis

Metalhorrors are easy to fight if you have EMP weapons. Because they don't adapt to EMP, they can be stunned indefinitely

Metalhorror infection

Once grey flesh is discovered, it is important to consider the pawns most likely to spread infections- Cooks, Doctors, and Wardens.

Tracing infections from an infected cook is nigh-impossible. Consider switching the entire colony to eating nutrient paste which will prevent meals from being an infection vector until the metalhorrors have been rooted out.
Doctors only spread infections while operating or feeding patients, which allows some guestimation as to who an infection might have been passed to. Do not schedule surgeries while a metalhorror infection is confirmed unless absolutely necessary. Pawns that have been downed and fed by doctors are susceptible to infection.
Permanently downed prisoners (e.g those with legs removed), and recently acquired prisoners recovering from being downed in combat, are highly likely to be infected by an infected warden. Thankfully prisoners can be interrogated and their infections uncovered- even by infected wardens.
Once a pawn has been confirmed as having an infection, if they share a bed or sleeping spot with another pawn, that other pawn will be infected.

Detection

Paramedics can never become infected or lie about test results, so they can be used to test for Metalhorror infections safely.

If you don't have a paramedic, the following procedure can be done after studying 2 pieces of gray flesh:

Have 2 doctors
The instant you become aware of a Metalhorror infection, have doctor 1 check someone other than doctor 2
If they find an infection, doctor 1 is clear.
If they do not, have doctor 2 check the patient
if they find an infection, doctor 1 is infected
If they do not, have doctor 1 check again
if doctor 1 finds an infection, doctor 2 is infected
if doctor 1 does not, then either both doctors are clear or both are infected.

Alternately, the player can systematically order every colonist to repeatedly conduct surgical inspections on a sacrificial pawn such as a prisoner. Eventually, the sacrificial pawn will be infected with a metalhorror which will be detected with a subsequent examination.

In the event of total infection, a sufficient number of Mechanoids can safely clear out the revealed Metalhorrors, as long as the Mechanitors they are linked to are still alive.

Force emergence by bed sharing

Since metalhorrors always emerge when they have infected half of your colony, and infection occurs as soon as two pawns share the same bed, you can trigger metalhorror emergence by letting your pawns share beds.

Some pawns must stay outside to fight the metalhorrors though. Since they may also be infected, each of them should stay in a different room to contain the potential metalhorror. These pawns should have good melee and doctor skills to tend your downed pawns afterward.

The number of participating pawns should be at least half of your colony to guarantee that the threshold is reached. Create a double sleeping spot in a separate room for every 2 participating pawns. Then create anethetize bills for each pawns and assign them to rest on the same spot (the game will say that the spot has been reserved, but just prioritize it anyway). You should assign pawns to sleep with someone who is not their lover or spouse, since lovers should already have infected eachother when they share the same bed before. If the threshold has been reached, metalhorrors should emerge after a few seconds. If not, swap the partners around until they emerge.

You can prepare for the emergence by armoring the pawns who have to stay outside and setting spiketraps in the bedrooms for the metalhorrors to trigger.

Prevention

Now as for preventing Metalhorrors from spreading premptively for the event of a infection, you can do the following

set a zone forbidding pawns from accessing prisons, kitchens and hospitals, and set that zone onto any pawn who has less then 30 days in their record, especially creepjoiners, or pawns who were attacked by revenants or any of the entities described in the summary, and keep note of the days in their record and set the zone off once the pathway has expired.
- Cooks can still butcher and cook pemmican safely and doctors can be left to treat animals if you separate those into different rooms.
- Slaves do not have a record for time spent as a colonist so stats like time spent under a roof can be used as a rough estimate.
- Colonists that were in the colony for over a year have their record set as #.# making keep track of them more difficult, the combat log can be used instead albeit those are prone to being wiped. ^[When?]
If a gray flesh event sets off then you can check any pawns who were assigned that zone.
For lovers you can place another bed in their room and assign the suspect to it, preventing the sleeping alone moodlet. a bedroll may be used instead to prevent the room's space stat from being reduced.
For combat encounters with entities you should ideally avoid having humans do melee combat, and let mechanoids and animals tank the hits instead.

Imprisoning Suspects such as Creepjoiners runs the risk of Prison Breaks and thus the possibility of outright losing them due to casualities or escaping so assigning a "Quarantine" zone to them until their drawback is identified can be a better alternative.

Mature metalhorror

You will fight groups of mature metalhorrors during the monolith awakening, they can do serious damage to your colony, but do not cause metalhorror infection.

Fighting metalhorrors are much like fighting scythers, due to their identical melee attacks and fighter role in combat. Tactics applies to scythers may also applies to them, and as they also vulnerable to EMP, and can be lured into spike traps. Metalhorrors are much faster and more resisting to damage than scythers.

Unlike scythers, however, metalhorrors are highly flammable. They can be ignited very easily, and will disengage from combat while on fire. A pawn armed with an incendiary launcher, molotov cocktails, or incinerator can easily cripple a pack of metalhorrors.

Bioferrite Harvesting

Due to the high containment requirements of metalhorrors and their sharp attacks, healthy ones are dangerous to maintain. However, legless metalhorrors can be captured with no risk of escape. They yield a decent 3.2 - 4.4 bioferrite/day depending on body size. If you find downed metalhorrors with damaged legs, continue to punch them with bare hands until both their legs are shattered, or death. Metalhorrors' high armor makes the first case more likely to happen than other entities.