-In Pathogen mod, you will face a TON of new monsters, including different main species, biome variants, incomplete forms...etc These creatures are evolutive, which means that depending on the biome, and the animal corrupted (explanations below),
 the mutant will be completely different, with different stats, abilities, resistances and even sometimes general appearance... Currently, the main mobs are prowlers, poisoners, walkers, marauders, raptors, infectors and enforcers. 
Each can adapt to the biome they're developing in. The 8 variants are jungle, mesa, swamp, ender, crimson forest, warped forest, aquatic and cave creatures.

Cave :


    -To evolve in complete darkness, this blind subspecies developped incredible abilities, even able to reduce its glow to not be spotted easily in the darkness. The lack of sunlight underground made this species skin colour completely depigmented and made all-sensing filaments grow on its back to better hunt in darkness. Cave variants are able to completely blind their prey while withering them but have no armor. 
Mesa : 


    -The mesa mutants, caracterized by being bulky and bigger than most are the most resilient of their kind. They can absorb a lot of damage and inflict long lasting effects.
Swamp :

    -The swamp mutants, caracterized by proeminent fangs and a lot of vegetation growing on their back, are a dangerous poisonous variants. The deadly venom coming from their teeth is a psychedelic nightmare for its foes, inflicting both poison and nausea. They tend to have lower health but greater speed and strenght than other variants

Jungle :

    -The jungle mutants, caracterised by lot of spikes and a thagomizer tail, are interesting creatures, the jungle poison bein a very different one, weakening the player and paralysing him... They tend to be a good balance between strenght health and speed
Aquatic :


    -Being prepared to every environement, the mutant kind is also able to thrive in aquatic ecosystems. The Aquatic subspecies will drain the target oxygen while dragging him down to the bottom of the ocean so be carefull while trying to kill one for its loot. An incomplete form will transform into an aquatic variant if its environnement is filled with water.


Warped forest: 

    -The warped forest mutants, caracterized by a more insect like appearance is a very unique variant. Being able to become totally invisible to hunt their prey, this subspecies developped a powerfull venom able to capitalize on the nether's accentuated heights... Warped poison is a combination of glowing, slowness and levitation effects
Ender :

    -The ender mutants, caracterized by a longer body and bigger horns is one of the most powerfull variant you may encounter. While being more resistant and dealing more damage than most mutants, its poison will completely negate any positive effects and will prevent your hardened steel armor from using its powers.
Crimson forest :


-As if the nether wasn't dangerous enough... This species is faster, deals more damage and has a stronger poison effect than every other mutant, but just like netherack, it really isn't very durable... Its poison is a combination of fire and wither

 Creatures :

For this section, we'll only show you pictures of the mesa variant, because there would be too many pictures to upload. Thank you for your comprehension.
Runners : 

-Coming from the corruption of a pig, a sheep, a cow, a horse or a donkey, runners are the most common mutants. Not having any particular abilities excepting their poison, they can be found almost everywhere...

Walkers :

-Result of the match between pathogen and either a piglin, a pillager, a player or a villager, walkers are amongst the most powerfull mutants. To compensate for their relatively weaker poison, those creatures are performing high knockback attack. You should take care about that, sometimes it can be quite surprising...
Poisoners : 

-This terrifying mutant lizard was well named... The poisoner is a hyper venomous creature, having the strongest poison effects of the entire mutant race. They come from the corruption of a witch or a spider
 Enforcers :

The tanky beast you're seeing now is named an enforcer. This may also be the last thing you'll see since this mutant is probably one of the most powerfull mutant of the mod. Don't underestimate this taurus looking monster, you'd be surprised by the ENORMOUS amount of damage he can do by just biting your ass. Add to that a very thick armor luckily letting projectiles go through, and you get one of the most tough to kill creature ever. They're the result of the corruption of a ravager or a hoglin

Marauders :


You have a strong armor that helps you fighting the hords of mutants ? Well that's not a problem for this guy. Possessing a high health an high melee, the marauder will inflicts fatal blows to your armor while poisoning you. And when I say fatal blows I mean it will ABSOLUTELY SHREDD IT. A netherite armor won't last long against these beasts, inflicting more than 40 times more damage to your armor than usually. It wouldn't be stupid to use a crappy armor without enchants to fight one, I'm sure you wouldn't appreciate loosing your full protection IV netherite armor on something like this... The marauder is the pathogen versions of a wolf or a fox
Prowlers :

Do not lower your guard because of the cat-like appearance of this mutant. Trust me, there is nothing worse than a prowler lurking in the shadow waiting for you to be close enough... This vicious creature will grab its prey in its jaws and crush it to death while strongly poisoning it, a good reason for you to stay away from them...
Raptors :

It seems like the pathogen has a weird de-evolutive effect on birds, retransforming them into the vicious pack hunters they once were. The raptor is a very unique kind of mutant since it exists in two different version : the Alpha and the Beta, the Alpha variant being bigger and stronger. Having little health, raptors are usually easy to fight, but when in pack, that's another story... If an alpha is near a group of beta raptors, they all receive a pack bonus, including increased strenght and an additional bonus effect depending on the biome type. Beta raptors will also inflict a poison effect to their prey if an Alpha is nearby, so take care of the big one first before you get shredded.
Infectors :

Let me introduce you to the world corrupter ! This rare mutant subspecies is highly agressive and will attack any viable host for the pathogen. Coming from the corruption of an enderman, this deadly mutant species will contaminate everything they touch, including terraforming biomes for their species.
Incomplete forms :


-After getting contaminated by pathogen, the contaminated creatures can eventually transform into intermediate forms which will later transform into a fully grown mutant, depending on the biome, and of course the species corrupted...

Weapons :

Ok so now we have big dangerous monsters roaming around the entire minecraft world. So how do we fight them ? Fortunately, Pathogen comes with some powerfull weapons you'll absolutely need if you want to rule your world again. Please notice that most of those requires netherite, so you better have plenty of it if you want to be truly hard to kill.
The katana :

The first weapon of our list is a classic weapon, made from hardened iron ingots, mutant bone and a biome ingot, this weapon has 8 variants just as the creatures themselves, each with their special effects. Fast and devastating, these blades are incredibly satisfying to use, the hardened steel helping the blade absorbing all the energy of the mutant essence. Also, this blade has a cool elemental-burning effect to lacerate your enemy with style. 
The Slayer :

Slayers are massive slow swords with a huge damaging potential, but a the cost of a slower swing speed. Just like the others, it comes in 8 biome variants, each with a special ability you can use by right clicking while wearing a biome armor, custom stats for each etc...
Battle hook :

A very versatile weapon that can be used as a sword, a pickaxe and an axe at the same time. This multitool deals moderate damages, has a relatively low swing speed and a powerfull poison effect depending on the biome variant. 

Pathogen armor set :

A relatively cheap armor made from incomplete moults and beast bones. This armor will prevent you from getting the pathogen sickness, wither effect and will give the player a haste bonus.

Scale armor :

This armor exists in 6 different flavours (jungle, swamp, mesa, ender,crimson and warped) each offering a different potion effect and a +20% damage increase with weapons of the same biome type(does not stack with any damage enchants)

Mutant Steel armor :


The mod's strongest armor, and you'll need it. An end game exoskeleton with incredible abilities. Every variants have in common a jump and speed boost with an immunity to the armor biome's poison effects and a +35% damage with the weapons of the same biome type. Each armor has additional bonuses depending on the biome type.

 Catalyst mecanic :

If you want to create all the mutant killing stuff of the mod, you're going to need hardened chitin ingots. In order to get this precious material, you have to combine a chitin horn, a phantom membrane and a netherite ingot in a new block : the catalyst. This uncraftable block can be found in altar-like structure spawning in most biomes. Just place the 3 ingredients in the specific slots and turn it on, the catalyst will use the power of lightning to merge them into a hardened chitin ingot.

Pathogen mecanic :

 

The pathogen is a black liquid you can find in your world. The contact between this fluid and minecraft wildlife will result in contaminating the subject. Infected mobs will later transform into an incomplete form, which is a highly agressive version of what they once were... The incomplete forms while not being very strong, are a real threat to your world, since they are one of the rare mutant species able to contaminate wildlife as well. After some time, incomplete forms will eventually transform into one of the fully grown mutant species depending on the biome they're in. It is important to note that they do not absolutely have to transform into a fully grown specialized mutant. If the biome they're in has nothing in particular like plains or forest, they won't transform  since they do not need it to survive