Enemy Expansion for Minecraft

Undead

Sprinter

An athletic undead who moves at 1.5x the regular speed of a normal zombie. Taking damage will slow him down, giving you time to deliver a combo attack or reorient yourself.

Slugger

A bodybuilding undead with 2.5x the strength of a regular zombie.
Beyond sheer muscle, hurting this guy will give him a short adrenaline boost, allowing him to charge at you. In this state, parry him with a shield, or strafe away from him. 

Senior

The bulkiest zombie of them all, the Senior retains the Slugger's adrenaline boost trait upon taking damage, though it can't utilise this very well with how slow and heavy it is. Be forewarned, though: This guy only grows stronger upon taking damage, gaining the ability to pierce through shields, and should be dealt with at a distance, in very good armour, or with supreme caution. Preferably some combination of those three approaches!

Equestrian

A fast and unpredictable enemy, this zombie's horse will lose all control upon taking damage and go into a blind frenzy. Be careful when dealing with this one. 

Frigid

A cold biome-exclusive undead, this poor zombie's legs were frozen off, leaving it to crawl around everywhere it goes.
Unfortunately for you, this means it can now fit through 1-block gaps. It'll also slow you down should it hit you, so don't touch it!

Meature

The crawling mutant head of a Zombie, the Meature is very much like a spider that'll hop to chew your flesh off. If no players are about, it'll instead target other undead. It can be neutralised and tamed when shown and fed Rotten Flesh, and will even fight alongside you! When it kills, it grows stronger, so it may be worth sticking by one to help it reach it's full potential. Sometimes, the Meature will spawn upon the head of a Zombie or Skeleton - When their hosts are killed, they'll hop right off to attack you, too. When killed, they'll sometimes drop themselves as Meat Heads to be worn, or to be cooked! To stop a Meature from teleporting to you when tamed, leash it and bind it to a fence post.

Huntsman

A more skillful Skeleton who's faster on his feet than his smaller counterpart. If you get too close to him, he'll punch you in the face to get you away!

Spectre

A supportive enemy spirit who will possess nearby undead, buffing them notably and bestowing them its robes. It'll jut right out again upon the mob's death, where it'll be vulnerable to being banished with a mere tap.

Gallant

A hacking and slashing possessed suit of armour that can quickly shred through you if you're not careful around it! While slow at first, sustaining more damage increases its resolve to kill you, and extensively its speed. It will also dash forward sometimes when hit, so be very careful! It rusts in water, slowing it down, so use this as a chance to retreat if needed!

Ghoul

A ghastly, sharp-edged creature of the cold who will tear you to bits should you get near it! Should you toy with it too much over its slow speed, it just might spit in your eye and blind you for a moment! It doesn't appreciate light melting the snow and ice of its biomes, and so will break torches and lanterns left on the ground! Or perhaps it's breaking them since it fears fire...? It burns to death much faster than your typical monster, so use that knowledge to your advantage!

Meatures, Sprinters, Sluggers, Seniors, Equestrians, Gallants and Huntsmen spawn in all biomes (besides deserts), whilst Frigid and Ghouls are cold biome exclusives.

Arthropods

Bugs! Everywhere!! Ahh!! 

Tarantula

A stronger Spider, the Tarantula will boost towards you upon taking damage, much like a Slugger. Sometimes, you'll be able to find them in the Dripstone Caves hanging upside down from the ceiling! In this state, they're harmless. If you aggravate them, however, prepare for a scrap.

Scorpion

With a preference for warmer climates such as deserts and Badlands, the Scorpion turns invisible upon taking damage. Keep track of it's glowing eyes, or face the consequences of a bout with poison and nausea.

Wasp

Out on their malicious business, the Wasp is found buzzing about Forests after dark. Try to avoid getting stung by them, as in addition to a variety of nasty effects, the resultant pheromone release also has a chance of summoning even more Wasps to dispose of you. Killing them yields their pheromone sack as an item, which can be thrown to summon a Wasp Drone that'll attack monsters! And you, if you provoke it. Don't provoke it, whatever you do!

Ladybug

A Lush Cave-dwelling arthropod with a sturdy shell, the Ladybug is a neutral mob who will pack a punch should you mess with it. Not only with you, but with undead mobs and spiders, whom it is endlessly hostile towards. Should a Ladybug fall in battle to an undead, it will be reborn as a Zadybug, who's a little slower than it's living counterpart, but something to watch out for nonetheless. If you feed a Ladybug Spider Eyes, there's a chance it'll spit Healing Goo back out at you, which can be thrown at allies to heal them, and undead to damage them! Additionally, this goo can be put into a bowl for Healing Goo Soup to replenish your own health pool!

Tarantulas spawn in all biomes, but most commonly in Dripstone Caves. Scorpions spawn in hot biomes. Wasps spawn in forests. Ladybugs spawn in Lush Caves.

Flies

Erratic little buggers who aren't very strong, but are very hard to hit! A single swipe of any sword should be enough to swat them without issue. Spawn in temperate and hot biomes.

Netherborn

Mobs from the Nether!

Cinder

The Nether's first and only new addition: The Cinder! Taking the place of every fifth Blaze, the Cinder is unlike it's daintier brother in almost every way - Where the Blaze hovers in the air and attacks from a distance, the Cinder floats close to the ground, rushing towards you to slice you to bits with its powerful, arrow-resistant shields. When hurt, it has a chance of shooting a small, explosive fireball - Signalled by it lighting up in flames. It's powerful helmet protects it from heavy damage, and upon its defeat will drop some of it in the form of Cinder Scrap: Use this precious metal by applying it atop a Netherite Helmet so that you may reap its benefits of increased speed when on fire, and a massive super-jump when touching lava!

Cave Dwellers

Mobs that spawn primarily or exclusively in caves!

Petrimen
Rocky humanoids who live exclusively in caves. They're all remarkably sturdy, resisting ranged and burning attacks exquisitely, and they all dislike your presence in their home thoroughly. Get out!

Silverking
Overgrown bedbugs who'll leak Silverfish when hurt, ew! Using a sword against them allows you to banish their silver spawn before they even have a chance to touch the ground, so consider making the most of that! They're cowardly, and get real fast when hurt. Might want to consider investing in Bane of Arthropods after all...

Intruder
A heavy-set Creeper variant who cannot be knocked back. With an even stronger explosion and the ability to survive its own blasts to boot, stay as far away from this guy as you can. If you HAVE to get close, make the most of your shields (which won't last long if you over-use them here.)

Crawler
A lightweight Creeper variant akin to the Intruder, this guy lacks health, strength and weight, but makes up for it in speed. It's light weight proves a benefit to it, as it can use its own explosions to propel itself through the air, making it hard to catch. Be careful around this one!

Troll
What could be considered a Warden progeny, the Troll can instantly kill a completely unprotected player in a single bite. Do NOT engage with it: When aggravated, it becomes briefly invincible, and massively faster. All things considered, the most sensible thing you can do to counter a Troll is to simply leave it be.

Vampire
This regenerative bloodsucker is a tricky bugger: With the ability to steal your health should it bite you, in addition to regenerating passively, the Vampire is slim and fast, allowing it to swiftly move in and momentarily slow and blind you should it sink it's teeth into you. When hurt, it'll either continue attacking, briefly and erratically run away, or turn into the Biter, a far weaker but more unpredictable bat form. After a couple of seconds, it'll have regenerated enough to turn back into a fully healed Vampire, effectively restarting the fight. Biters are most effectively taken out by Trident throws and fully-charged axe swings, but both Vampires and Biters can also be banished by being burnt with flames, achievable with either fire-based enchantments or being right-clicked with Flint and Steel. Additionally, they'll also combust under broad daylight - Don't get caught in the blast when the sun rises!

These mobs spawn in all biomes, but just locked to the underground by default. This is configurable.

Goblins

They're a cowardly bunch, avoiding Iron Golems like the plague, but have the unique ability to regenerate health when wet, be it in rain or the ocean.

Thief
Creeping around low to the ground is the Thief, who will steal your XP and run when you're not looking! They'll have a chance to flee when hurt, dropping some XP along the way, and killing them will balance things out, with any luck, as they drop not only a lot of XP, but Bottles O' Enchanting, too!

Bouncer
A self-serious fellow with no time to waste, the Bouncer will calmly walk up to you, before kicking you right in the... Potion bottles. Yeouch!

Baker
A Gabble of Goblins has to eat SOMETHING, and what better than freshly baked cake from their local Baker?
Unfortunately, Goblin Bakers also specialise in demolitions, so their cakes were actually made in a factory: A BOMB factory. They're BOMBS.
Their Suspicious Slices have 1/6th of a chance to BLOW YOU UP should you eat them! The other 5/6ths of the time though, they'll give you Regeneration.

Is it worth it? Choose wisely!

Rancher
One efficient means of transport for a Goblin is the elusive Slime, which the Rancher is a specialist in controlling.
With it, it can launch great heights up into the air, and even throw slime balls at you to slow you down! If only it wasn't so unyielding for it to control...

Errant
If the Bouncer provides the group security, the Errant enforces the law, and the law demands: No humans shall go unpunished for walking 16 blocks within a Goblin's vicinity! Wielding a mighty axe, they clumsily swing at you in the hopes that it'll butcher you. Keep your cool, though, as their slow speed and tendency to lose their nerve during battle can get the better of them. At least they're brave enough to deal with their undead counterparts!

Caster
What could be considered the de-facto head-honcho of any Gabble of Goblins, the Caster's magic spells have the ability to puppeteer you mid-air, so make sure you avoid their projectiles at all costs! They can actually be effectively deflected with a shield, so use that to your advantage. When not targeting players, Casters are on the look-out for villagers to transform into new Goblins, so that they may join their nomadic ranks.

Zobgoblin
They frighten the life out of living Goblins, and will run away at the drop of a hat; Zobgoblins are not too troublesome to deal with. Just beware that like Thieves, they'll slow you down for a moment should you get touched by one.

Thieves and Zobgoblins are all-biome mobs (besides hot biomes), whilst the rest are Swamp exclusive.

Animals

Flutterfly

A beautiful colony of regenerative butterflies that spawn in all biomes who'll heal you when touched with a right-click, and wither you when attacked! They bunch up together to scare off potential predators... But who would want to hurt creatures so good and pure?

Bull

Desert/Badlands/Savannah-exclusive Cow who will attack Husks and fight back against those who dare bring it harm! They could make for great allies if you plan on living in the desert.

Boar

Taiga-exclusive Pig who will attack Players and run from Zombies should they get too close! Little cowards...

Rooster

Jungle-exclusive Chicken who will hurt you if you dare hurt it! They're not afraid to fight any Foxes, Wolves, Ocelots or Cats nearby, so keep them well-guarded if you've got a pet puppy about...

Ram

Peaks/Mountains-exclusive Sheep who will knock you far and away should you try and harvest it for its meat! It's thick wool gives it a little armour, and when sheared, regrows quickly and consistently compared to a Sheep's speed of wool regrowth. Rams are not fond of Zombies or Skeletons, and will attack either on-sight.

Seabound

Angler

A small but swift menace of the seas, these frightening, aggressive little guys will turn invisible when attacked and panickedly swim away - Not that it does them much good, as their prey-attracting bulbs give away their location! Despite their speed, they maintain low health pools, and can be dispatched quickly with good gear. Whilst typically unpleasant to be around, they especially love the taste of Drowned flesh, and just might assist you in battle should the circumstances befit them! They can be found in all Deep Oceans besides Warm ones.

Kelpie

Harrowing behemoths of the depths, Kelpies can drag you down to the bottom of the sea with their extending tongues. If hurt, it will summon speed-boosted Drowned to try and dispatch of you as it attempts to regain it's composure. Don't lose sight of it and manage it's minions for the chance at earning a Heart of the Sea!

Piecrab

Although outwardly tough, if a Piecrab is hurt enough, it'll eventually leave you alone! They're good swimmers, and allow whatever monster rides it to make chase towards you rather effectively! They can be killed for a Crab Pie, which grants Resistance briefly when eaten cooked.

Gladius

A giant Squid that's gotten too smart for it's own good - Having learnt to adapt outside the water, the Gladius is coming straight for you. Fortunately for you, it's squishy body makes it easy to push away. Knocking it back into the water whence it came will force it to adapt its body for the liquid realm, turning it into it's smaller Gladilad form. Unfortunately for you, both iterations of the mob retain the classic ink-spray technique carried down from their Squid ancestors, and will use it to blind you as often as possible. Shield your eyes! Spawns by beaches and rivers.

And More!

Propeller

Mobile dummies made of copper and iron that can shoot arrows at you and fly away when the going gets tough! Fear not though: A well-placed arrow can take them out of the sky very swiftly, in addition to nabbing you an achievement! If caught in the rain or a body of water, they'll oxidize and become far slower. Spawns in all biomes.

Wolfsbane
A big bad werewolf of purple proportions, the Wolfsbane starts out as a slow, lumbering enemy who's heavy damage can be negated by its slow speed... That is, until it sustains enough damage to become notably angrier, at which point it'll stand down on all fours and charge for you. Attacking it in this state will inspire it to lunge, which can be used to your advantage to keep it away whilst it's in a mania. Spawns in all biomes.

Cockatrice
A swift, giant chicken with a dragon-like lower half, this foul foul can almost freeze you in place with an up-close-and-personal stare in the eyes, in addition to poisoning you significantly upon a bite, too. Occasionally, They can be found with skeletons riding atop them - Said Skeletons cannot handle the force from a Cockatrice's great leaps into the air, however, so using this to your advantage would be wise. Just like their tiny natural counterparts, they drop Chicken on death, making for a great food source whilst stuck underground. Spawns in all biomes, underground exclusive.

Reaver

This malformed, Illager-born beast of the skies acts as the perfect mode of transport for any patrolling Pillager who needs to keep out of your effective range. Fast as they are deadly, the Reaver will weave around and above you, allowing the Pillager on it's back to take care of you from a distance. If you happen to kill the Pillager before the Reaver, it will come for you far more directly. Try and take it out first! Only spawns alongside Pillagers with the Pillager Spawns With Reaver Chance config option.

Dreadnought

An otherworldly, shadowy creature emerges from the darkness with the sole purpose of hunting you down... While it may seem unkillable, it will leave you alone if you either pelt it with enough damage, or expose it to the light. Veer well-clear of it!

Armour

Meat Head - When worn, gives permanent Jump Boost, in addition to a short speed and strength boost at the cost of inflicting Hunger when damage is taken. Drops rarely from a Meature. 

Phantasm Cowl and Cape - Crafted from Phantom Membrane and other materials, become the night and speed through it whilst partially invisible and fully able to see via Night Vision! When crouched, you'll gain Slow Falling, making this set perfect for exploring dark caves! Watch out, though: This set becomes useless as Leather when used in the light.

Cinder Helm - Gain the power of a Cinder and become faster when burning! Also gain the ability to hop on lava! Neat!

Slimehead - Repel attackers and bounce them back with this head made of gelatin! Drops rarely from a slain Rancher.

Silverhat - Spawn ally Silverfriends who'll nibble on monsters on your behalf when hurt! Drops rarely from a slain Silverking.

Headbiter - Receive a short dose of speed and healing when attacking! Rarely drops from a slain Biter.

Spiderlatch - Grants poison-inflicting attacks and poison immunity to the wearer.

Trollface - Grants 5 points of knockback immunity (for reference, 1 piece of Netherite gear gives 1 point of knockback immunity.)

Spectral Hood and Robe - Wearer can inflict a moment of Blindness and Weakness respective to the armour piece worn. Either one makes a Spectre spawn upon the wearer's death.

Bull Skull - A little knockback resistance goes a long way!

Flutterfliers - Gain the power of regeneration when hurt whilst wearing these wings!

Horsehead - Gives the wearer 10 seconds of both Speed III and Hunger III when the wearer is hurt!
Brutish Garment - Gives the wearer 5 seconds of both Resistance III and 10 seconds of Hunger III when the wearer is hurt!
Mini-Wither - Attacks from the wearer deal Wither III for 3 seconds!
Banemask - When hurt, the wearer will be compelled to perform a small leap (even in the air), just like a feral Wolfsbane! Parkour potential, anyone?
Gladling - A baby Gladius that spits ink at whoever attack it and it's host! Causes the host to experience knockback akin to an actual Gladius.

Items

Cinder Scrap - Used to craft the Cinder Helm, drops from Cinders.

Wasp Pheromone Sack - Dropped from a Wasp, when thrown it spawns a Wasp Drone, who'll fight monsters on your behalf before quickly dying.

Healing Goo - Can be thrown at allies to heal them, and undead to harm them! Gained from feeding Ladybugs Spider eyes.

Healing Goo Stew - Crafting from Healing Goo, drink up for a wonderful source of healing!

Suspicious Slice - A Goblin-baked slice of cake that has a 5/6 chance to give you regeneration, and a 1/6 chance to BLOW YOU UP! The choice is yours.

Preposterous Portion - Only for the hungriest of players. Do NOT eat it.

Crab Pie - When cooked, gives Resistance for 10 seconds! 

Notes

- Common mobs in the caves and deepslate caves are replaced by special cave variants. You can turn this behaviour off with the Replacement Rule config options. If you turn them off, the mobs will still spawn, just far, far more rarely.

- Certain mobs are designed to be cave-exclusive. You can allow them to spawn above ground by turning off the Y-level Restricted Spawning config options. Might work well in conjunction with turning off the replacement rules.

- Groups of Goblins are known as Gabbles, and their group-spawning behaviour is controlled by the Gabble entity, which in of itself is empty, and exists to spawn in the Goblins before itself disappearing. Disable the Gabble from spawning if you don't want Goblins spawning in groups.