Metalhorror

The Metalhorror is an entity that can threaten your colony. It will infect your colonists one by one and burst out 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 other creatures, creating more of themselves as they do. It is possible to test pawns in order to find out who is hosting a Metalhorror. Upon detection, Metalhorrors will cut their way out of their hosts, leaving them wounded and bleeding. The death of their host will also cause them to emerge, even if they have not been detected first.

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.
During revenant hypnosis
The melee attack of a shambler, fleshbeast, noctol, or sightstealer.

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.

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 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 sleeping 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]} It is not known whether this infection vector persists after the originating infections are revealed.^{[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 a meal to a patient can infect the patient. This includes hemogen packs being fed to hemogenic prisoners and patients.	30%

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 4.4 bioferrite and 220W per day.

Combat

When attacked, metalhorrors only receive 25% of damage.

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?]

Melee Attacks	Damage Amount	Cooldown
Cut	20	2.0 sec

Unlike scythers, however, metalhorrors are highly flammable. They can be ignited very easily, and will disengage from combat while on fire.

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

Analysis

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 is virtually guaranteed to be infected as well.

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.

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.