Ghoul

Ghouls are humans that have been warped into powerful, twisted combat entities with very few needs. Ghouls can appear as both enemy units and become a part of your colony. Ghouls that are part of your colony can only eat raw meat and fresh corpses. Captured Ghouls do not require food.

Acquisition

The only way to acquire friendly ghouls is to start with one, or perform ghoul infusion after researching Ghoul Infusion in the Anomaly tech tree. This will damage faction relations if performed on a prisoner.

Summary

A ghoul is effectively a colonist that is limited to only melee attacks. They cannot wield weapons or apparel, do any work, take drugs or use any special ability they had in life. Ghouls can be restricted to zones and drafted like normal colonists. In combat, they can be directly commanded to melee attack or use the ability provided by ghoul-specific body parts. Ghouls will fight adjacent fires, but do not seek out fires to extinguish. All Ghouls are capable of violence no matter their backstories, traits, or genes.

Properties

Ghouls do not age at all, even if not yet at maturity. Note that this means that ghouls created from younger pawns will never have the full body size and body part health of an adult. Ghouls can have age related heart attacks. They retain most properties they had in life:

Melee and Shooting skills (even though ghouls can't shoot) and passions are retained. Other skills and passions are disabled.
Traits and backstories are retained, this can cause a ghoul to be incapable of firefighting.
Hediffs are retained, including void touched.
Body types and non-cosmetic genes are retained. After converted, they can still undergo gene extraction or be implanted with new xenogerms. Due to the low cost of ghoul resurrection serum, ghouls can be killed and resurrected to bypass the gene regrowing time.

Ghouls retain the natural attacks of a human, and also gain a left and right claw attack and an additional bite attack.

All ghouls are given two hediffs that implement the majority of the stat changes experienced by ghouls. These hediffs are "Ghoul" and "Regeneration".

Ghoul:

Pain: ×0%
Max Nutrition: 2
Psychic sensitivity: ×0%
Minimum Comfortable Temperature: −40
Maximum Comfortable Temperature: +40
Minimum Containment Strength: +35
Talking: ×0%

Regeneration:

Regenerate 100 HP/day

Separate from these hediffs, ghouls also don't bleed when injured. The regeneration hediff heals the ghoul's earliest-applied injury at the rate of 0.1 HP/s. After it's fully healed, the hediff will move to another injury at random to heal. Lost body parts will be converted to wounds and healed. It's also separate from the natural injury healing.

Needs

Ghouls can only eat raw meat and fresh corpses. They will automatically try to eat available food in their assigned zone. Friendly ghouls that are not fed will eventually betray the colony, never becoming friendly again. Once their food need reaches Once their food need reaches 0, and hidden Meat hunger hediff will appear and worsen over roughly 24 hours. The more extreme this hediff is, the more likely the ghoul will betray.

Other than food, ghouls have no other need, mood, or relationship. Other needs created by genes or addiction will be disabled. They can't have mental breaks and won't be counted as a colonist for things like the recluse trait.. Despite the in-game description, colonists do not gain negative mood for being near a friendly ghoul, however they will experience a negative mood if a loved one becomes a ghoul or spawns as a ghoul.^[Detail]

Ghoul-specific Upgrades

Ghouls can have normal human body parts installed. However there are also some ghoul-specific upgrades available by researching Ghoul enhancements in the Anomaly tech tree:

Adrenal heart — Passively increases hunger, grants an ability to gain a burst of ×0.7 attack cooldown and +4.00 movement speed for 15 seconds. The cooldown is 29.17 seconds.
Corrosive heart — Allows the ghoul to spew acid on a 2 hour cooldown, but only has 85% part efficiency
Ghoul barbs — Increases melee damage by ×150% at the cost of −0.25 speed
Ghoul plating — Incoming Damage Multiplier ×0.5 at the cost of −0.75 speed.
Metalblood heart — On a 6 hour cooldown, gain the Metalblood hediff for 40 seconds, which gives ×50% damage resistance and ×400% fire and burn vulnerability. This hediff does not stack with the metalblood serum.

Ghouls can be administered serums, but not drugs. They aren't affected by any mood effect by serums.

Analysis

Ghouls are incredibly powerful guard dogs and melee attackers:

With melee upgrades of ghoul barbs, power claws, juggernaut serum, and strong melee damage gene, their attacks will destroy any body part of any human they hit (no matter the armor), frequently one-hit killing enemies in cataphract armor.
With metabolic upgrades of nuclear stomach, +5 metabolic efficiency, and robust digestion gene, they need less than 4 twisted meat per day to survive.
Due to their regeneration and the affordability of ghoul resurrection serum, it's safe to use ghouls as tanks, or even let them die in combat.

Converting a colonist into a ghoul is a good way to make use of an otherwise terrible pawn or a colonist you can't save from death. The converted ghoul will quickly regrow lost limbs and self-cure detrimental health conditions.

A ghoul makes excellent bait to lure sightstealers, as they can remain patrolling outside forever.

While requiring direct control, Ghouls can still help with some work in colony. While drafted they can be used to hunt animals (though they will not carry the corpses back). They can also be used to fight fires. In Anomaly starting scenario the Ghoul allows you to skip early defences, indirectly reducing amount of work that needs to be done.

Be especially careful when engaging enemy ghouls in melee combat. They will not be forced down due to pain, so they will fight much longer than regular human raiders.

Body parts

Ghouls can also make effective use of body part weapons like the power claw. As they cannot hold conventional weapons, ghouls can only make unarmed attacks. Implanted weaponry offers them a powerful upgrade, making their already powerful strikes terrifyingly effective in combat.

Combing Ghoul barbs, the strong melee damage gene stack with the increased dps of the implants and offer dps comparable to high tier melee options.

The power claw features the highest damage, albeit with a small movement speed penalty.

If it is not possible to give a ghoul two power claws, it is better to give them one power claw and one wooden hand than to keep the normal hand. This is because it would choose the weaksauce normal fist 25% of the time, thus reducing the damage, but with a wooden hand it will only use the power claw.

If you can't produce metalblood serums, the metalblood heart is a good upgrade for your ghouls. But if you can, upgrade your ghoul with adrenal heart for a boost to melee damage and speed or corrosive heart for the acid spray attack

Ghoul melee damage at melee level 20 and no other hediff or gene
Upgrades	Melee DPS	Melee AP
None	3.29	11%
1 Power claw	8.28	28%
Power claw + Wooden hand	9.64	33%
2 Power claws	9.90	33%
Ghoul barbs	4.93	16%
Ghoul barbs + Juggernaut serum	7.39	25%
Ghoul barbs + Strong Melee Damage	7.39	25%
Ghoul barbs + Juggernaut serum + Strong Melee Damage	11.09	37%
Ghoul barbs + 1 Power claw	12.42	41%
Ghoul barbs + Power claw + Wooden hand	14.45	49%
Ghoul barbs + 2 Power claws	14.85	49%
Barbs + Juggernaut + Strong Melee Damage + Power claw	27.72	92%
Barbs + Juggernaut + Strong Melee Damage + Power claw + Wooden hand	32.52	111%
Barbs + Juggernaut + Strong Melee Damage + 2 Power claws	33.52	111%

Genetics

Ghouls primarily benefit from genes that improve their Incoming Damage Multiplier, melee skill and damage, movement speed, and achieving a good metabolic rate to reduce meat consumption. Ghouls will inherit genes from their underlying xenotypes, meaning that some make for better ghoul candidates than others.

Below are all genes that have positive effects on ghouls. Other genes either have negative effects, no effects, or only positive in term of metabolic efficiency

Good Genes
Gene	Improves	Metabolic Cost	Commentary
Robust	×75% Incoming Damage Multiplier	−2	Reduces damage taken by ghouls, improving their capability to soak incoming damage for longer.
Strong melee damage	×150% Melee Damage Factor	−2	Increases damage dealt by ghouls
Naked speed	+0.1 Movement speed	+2	Slight increase to movement speed while giving free metabolic efficiency
Fast runner	+0.2 Movement speed	−3	Double the movement speed bonus of Naked Speed
Very fast runner	+0.4 Movement speed	−5	Huge increase to movement speed, but very metabolically costly.
Strong Melee	Melee Skill +4	−1	Improves Melee skill which boosts melee hit chance and melee dodge chance
Great Melee	Melee Skill +8	−3	Larger Improvement to Melee skill
Unstoppable	Stagger Time Multiplier ×0%	−2	Removes stagger from receiving damage
Fire Resistant	Flammability ×10%, Flame damage ×25%	−2	Resist flame damage and avoid being set on fire
Robust Digestion	Raw Nutrition Multiplier ×180%	−1	Increase nutrition given by raw meat
Elongated Fingers	Manipulation ×110%	−1	Slightly increase manipulation, which affects melee hit chance
Smooth Tail	Manipulation +5%	−1	Slightly increase manipulation
Superfast Wound Healing	Injury Healing Factor ×400%	−3	Quadruple the normal healing factor to roughly 25 HP/day

There are many genes whose negative effects don't affect ghouls at all, thus they can be used to improve their metabolic efficiency. Some of the notable genes are:

Free Metabolic Efficiency
Gene	Changes	Metabolic Cost	Commentary
Awful Skill	Skill −8	+2	Ghouls only use Melee skill, any other skill can be ignored
Poor Skill	Skill −4	+1	Ghouls only use Melee skill
Hyper-aggressive	Mental Breaks and Social Fights	+3	Ghouls don't social fight or have mental break
Aggressive	Mental Breaks and Social Fights	+2	Ghouls don't social fight or have mental break
Very Unhappy	Mood Penalty	+5	Ghouls are unaffected by mood penalties
Unhappy	Mood Penalty	+3	Ghouls are unaffected by mood penalties
Deathrest	Need for deathrest	+6	Ghouls don't need deathrest
Hemogen drain	−8 Hemogen per day	+6	Ghouls don't need hemogen
Pyrophobia	Fleeing fire mental break	+4	Ghouls don't have mental breaks

Hunger management

Ghouls don't get cancer, so the nuclear stomach is an ideal way to keep them from berserking from hunger.

The Robust digestion gene synergizes very well with the Ghouls natural diet of raw meat, but don't work with corpses^[Verify]

Ghoul made from body-mastery creepjoiner don't need to eat at all, but removing of sleep and comfort needs became redundant.

Medical quirks

Because ghouls rapidly regenerate their organs, you can harvest their organs before turning them into a ghoul:

Harvesting a spare lung and kidney is possible for normal pawns.
You can harvest all six organs from a sanguophage.
If you have a detoxifier lung and kidney, you can install them to the pawn and harvest both natural lungs and kidneys. Then after the ghoul has finished regenerating, you can safely remove the artificial organ.

Becoming a ghoul does not remove duplication sickness, paralytic abasia or cirrhosis. However, if you then euthanize the ghoul and revive them with a ghoul resurrection serum, it does remove the sickness but won't cure the paralytic abasia.

The Ideal Ghoul

Here is the setup for the best ghoul that can be mass-produced by an advanced colony. The follow features are very hard to achieve; but once achieved, they can be duplicated using the Corrupted obelisk any number of times:

Void touched: available during the Anomaly ending, gives 100 hp/day regeneration on top of ghoul's regeneration.
Level 20 melee skill: massively improve melee hit and dodge chance.
All keystone and good genes listed above, except for Strong Melee and Great Melee, as they have already been covered by the base melee skill. Other metabolically efficient genes should be included to bring the efficiency up to +5.
Tough trait: Incoming Damage Multiplier x50%.
Jogger trait: Move Speed +0.4.
Nimble trait: Melee Dodge Chance +15. This gives a small increase in the final melee dodge chance and can be skipped.
Trauma savant: arguably the hardest to achieve, while only giving a very small improvement for melee hit chance.

Once you have a colonist or slave with these features, duplicate them using the Corrupted obelisk and turn the duplicate to ghoul, keeping the original. The ghouls can have these body parts installed to upgrade them further:

Ghoul plating: Incoming Damage Multiplier x50%, while Move Speed -0.7
Ghoul barbs: Melee Damage Factor x150%, while Move Speed -0.25
Adrenal heart: gives a massive buff for move speed and melee damage when used.
Power claws: greatly improves ghouls' melee damage.
Nuclear stomach: Food Consumption x25%.
Stoneskin gland: sharp armor +70%, blunt armor +30%, heat armor +50% while moving x85%. This will also be the final armor values of the ghoul.
Regular Juggernaut serum administering: Move speed +0.5, Melee Damage Factor x150%, Injury Healing Factor x200%.
Metalblood serum administering: Incoming Damage Multiplier x50%, while flame and burn weakness x400%. The flame weakness is cancelled out by the fire resistant gene.
Healing enhancer: natural healing factor x150%.
Bionic eyes and legs: improve melee hit and dodge change, and also move speed. These can also be skipped without reducing the power of the ghoul by much.

Note that power claws, bionic eyes and legs may be destroyed in combat if they take too much damage, so be ready to replace them if you decide to give to the ghoul. Other body parts are less likely to be lost as the ghoul are more likely to be downed or die before that. Overall, the ghoul would have these stats:

Daily Food Consumption 0.32 with Raw Food Multiplier x180%: this means they need only 3-4 twisted meat per day to live.
Healing 200 hp/day, plus roughly 75 hp/day from the 800% Injury Healing Factor and 150% Natural Healing Factor.
Incoming Damage Multiplier 9.4%: this improves the amount of damage ghouls can take by over 10 times, which means it takes roughly 2925 damage point/day, or 2.9 point/s (after armor and melee dodge) just to negate the healing effect of the ghoul. In practice, the ghoul can fight an infinite horde of Chimera one by one.
Melee AP 111%.
Melee hit damage 74.25, for a DPS of 34.41 (without Ghoul frenzy), or 49.16 (with Ghoul frenzy).
Melee Dodge Chance 38%.
Move Speed 4.7 (without Ghoul frenzy), or 8.42 (with Ghoul frenzy), or 10.86 (with Ghoul frenzy and psychic focus).