MetaDoom

MetaDoom is a randomizer gameplay mod by Kinsie, that serves to add elements from several games in the DOOM series, including mainline games, spin offs, ports and the press release beta.

The mod adds new sounds, sprites, effects and gameplay changes to resemble and reference multiple DOOM games while still trying to keep some balance within the core gameplay.

While introducing content such as new weapons and enemies, the mod has a special randomization system that handles the placement of the weapons and enemies, in which it can be affected by the player's progression through the maps.

The weapons in MetaDoom come in a form of a big and diverse arsenal that not only expands the number of weapons, but also gives most of them secondary fires, while also adding inventory items that can be discovered near other items.

The additional enemies in MetaDoom come with different designs and abilities that can replace regular enemies, althought the Hellknights, Barons of Hell and Cyberdemons are fully replaced with some of these additional enemies rather than just being replaced at certain times.

A noticeable feature in the mod is a score tracker, which is a nod to an unused feature intended for the original Doom, that can be affected by either killing off enemies or picking up treasure items, that will either replace or spawn next to armor and heath pick ups.

Weapons

 * EMG Sidearm: Based on the Pistol from Doom (2016). Primary fire shoots an infinite ammo, low damage projectile. Secondary fire toggles a flashlight on and off, allowing visibility in dark areas.
 * Chainsaw: Based on the Chainsaw from Doom (2016). Primary fire activates it in the same manner as its classic counterpart. Secondary fire delivers a horizontal swing that deals high damage.
 * Combat Shotgun: Based on the Shotgun from Doom 64. Primary fire shoots a normal buckshot. Secondary fire uses 5 shells and launches a grenade that explodes on contact, similar to the Explosive Shot mode of the shotgun in Doom (2016)
 * Super Shotgun: Based on the Super Shotgun from Doom II. Primary fire shoots a large blast consuming 2 shell. Secondary fire is identical.
 * Assault Rifle: Based on the Machine Gun from Doom 3. Primary fire shoots bullets rapidly. Secondary fire switches to a Micro Missile rack, which uses 3 bullets instead of 1, but is much stronger, like the Heavy Machine Gun in Doom (2016).
 * Rocket Launcher: Based on the Rocket Launcher from Doom (2016). Primary fire shoots a rocket. Secondary fire detonates the rocket in mid-air.
 * Plasma Rifle: Based on the Plasma Rifle from Doom and Doom II. Primary fire shoots plasma blasts like in Classic Doom. As with the Heat Blast upgrade from Doom (2016), firing the Plasma Rifle fills up a meter on the gun's screen. Once all 5 bars are lit up, secondary fire releases a shockwave.
 * BFG 9000: Based on the BFG 9000 from Doom (2016). Primary fire is the classic green plasma ball which does extreme damage. Secondary fire shoots a bunch of smaller blasts, much like the BFG in the pre-release versions of Doom 1. Unlike Classic Doom, but like Doom 3 and Doom (2016), the BFG uses seperate ammo from the Plasma Rifle.
 * Holy Water Pistol: Taken directly from Doom II RPG. Primary fire squirts some holy water out, making demons that come in contact run away in panic. Secondary fire drinks from the Holy Water Pistol, restoring some health points at the cost of 3 ammo. The Holy Water Pistol can be refilled by simply standing near water or even toxic waste.
 * Fire Axe: Based on the Axe from Doom RPG. Primary fire swings it, doing good damage and making a few small health pickups drop from the damaged enemy. Secondary fire is indentical. The Fire Axe kills zombies instantly and destroys barrels without exploding them.
 * Chaingun: Based on the Chaingun from Doom 64. Primary fire revs it up before firing. Secondary fire activates a turret mode, like in Doom (2016). Firing while in turret mode results in an insane fire rate, but uses bullets quickly, even with full ammo extended by a backpack, and the player cannot move while in turret mode.
 * Gauss Cannon: Taken directly from Doom (2016). Primary fire launches a blast similar to the Skulltag Railgun. Secondary fire activates a scope for increased accuracy.
 * Fire Extinguisher: Taken directly from Doom RPG. Primary fire sprays it ahead, instantly killing Lost Souls and taking out fire-based projectiles, such as Imp fireballs and Mancubus blasts, as well as putting out torches and burning barrels. Secondary fire sprays it directly on the player, used for avoiding Archvile attacks.
 * The Unmaker: Taken directly from Doom 64. Primary fire shoots lasers. As in Doom 64, demon keys, found in areas where the BFG spawns, can be picked up to increase the number of lasers shot from 1 to 3. The secondary fire, only usable once the player has collected at least one demon key, briefly charges the Unmaker before it shoots a very strong beam.
 * Soul Cube: Taken directly from Doom 3, but its sprite is a Spawn cube. Primary fire launches the Soul Cube forward, destroying any foe in its path and turning them into health and ammo pickups. Secondary fire is the same. As in Doom 3, the player must pick up soul essence dropped by killed demons to power up the Soul Cube.
 * Grenade Launcher: Taken directly from Doom (2016)'s multiplayer. Primary fire launches a grenade that bounces around, exploding when it lays to rest or touches a demon. Secondary fire shoots a different grenade that releases a gas cloud, which lingers for a bit, doing damage on contact.
 * Lightning Gun: Taken directly from Doom (2016)'s multiplayer. Primary fire shoots a close range stream of electricity. Secondary fire shoots a projectile that stuns enemies it hits.

inventory Items

 * Hand Grenade: Taken directly from Doom 3. These bounce on the ground before exploding for a short amout of time, although they can explode when in impact with enemies
 * Tesla Rocket: Taken directly from Doom (2016)'s multiplayer. When used, the Tesla Rocket begins to hover in the air while damaging nearby enemies in with a stream of electricity similar to the one from the Lightning Gun. These can also explosed when in impact with a wall.
 * Siphon Grenade: Taken directly from Doom (2016). When thrown, these cause a blast that not only freezes enemies for a short amount of time, but also damages them, while the player regenerates health.
 * Shield Wall: Taken directly from Doom (2016)'s multiplayer. The Shield Wall activates a solid blue lighted barrier, that can prevent attacks from both enemies and the player for a short amout of time.
 * Dog Collar: Taken directly from Doom RPG. This item can only be used on the demon dog enemies (these being Hellhound, Cerberus and Demon Wolf), which will then turn the enemy into a melee weapon that, when used, can gain armor points while attacking enemies. This melee weapon can be thrown, which will then explode, causing damage upon enemies
 * Hologram: Taken directly from Doom (2016). Upon activation, it generates a refracted-light hologram of the player's character that attracts enemies

Enemies

 * Hell Razer: Taken directly from Doom (2016). these replace the zombieman and are able to charge up and fire a stream of argent energy that causes damage.
 * Z-Sec: Taken direclty from Doom 3. These are able to do a quick roll and crouch. which can help them avoid attacks from the player.
 * Nightmare Imp: Taken direclty from Doom 64. These translucent blue/purple imps not only move faster than the average Imp, but their fireballs are faster as well.
 * Imp Lord: Taken direclty from Doom (2016) and named after an enemy from Doom RPG. These can teleport quickly, which can make it harder for the player to kill them.
 * Hellhound/Cerberus/Demon Wolf: Taken direclty from Doom RPG. These are able to move and attack faster than the regular Pinky Demon, while also being able to jump. These can also be turned into a melee weapon with the Dog Collar.
 * Bull Demon: Taken directly from Doom 3 and named after an enemy from Doom RPG. They can charge at the player, much like the Pinky Demons from Doom (2016)
 * Nightmare Spectre: Taken directly from the PlayStation version of Doom. These are dark cyan tinted version of the Spectres that can move faster and cause more damage.
 * Phantom: Based on an unused version of the Lost Soul and named after an enemy from Doom RPG. These can strafe in the air and shoot a small green projectile.
 * Wretched: Taken direclty from Doom (2016) and named after an enemy from Doom RPG. these can use their tongue, will can not only cause damage but also throw the player in different directions
 * Malwarth: Taken direclty from Doom 64 and named after an enemy from Doom RPG. these have the ability to shoot 3 fireballs.
 * Baron of Hell: Taken direclty from Doom (2016). They fully replace their classic counter parts. These are able to jump and slam on the ground, which creates red damaging flames and can throw a red fireball that splits into 4 green fireballs travelling through different directions
 * Hellknights: Taken directly from Doom (2016). They fully replace their classic counter parts. These are faster than the Barons of Hell and can jump higher, but their slams attacks and projectiles are weakers.
 * Former Commando/Lieutenant: 2 classic chaingunners named after 2 enemies from Doom RPG. The commando carries the Chaingun, while the Lietenant carries the Assault Rifle.
 * Former Assassin: Taken direclty from Doom 3 and named after an enemy from Doom RPG. These can throw a tentacle arm in the same manner as the tongues from the Wretched.
 * Fiend: Taken directly from Doom (2016) and named after an enemy from Doom RPG. these are able to aim and shoot multiple rockets while also able to hover, much like the Revenants from Doom (2016).
 * Rahovart: Taken direclty from Doom 64 and named after an enemy from Doom RPG. These are able to spawn at least 2 Lost Souls at a time.
 * Beholder: Taken directly from Doom RPG. These can spawn muiltple Forgotten Ones at a time.
 * Forgotten One: Named after an enemy from Doom 3: Resurrection of Evil. these are smaller and weaker Lost Souls that originate from the Beholder.
 * Cyber Demon: Taken direclty from Doom 64. The Cyber Demon can charge to move away quicker from one area to another, much like the Cyber Demon from Doom (2016).

Trivia

 * Some of the additional enemies have names inspired by enemies from Doom RPG, for example: The Pinky Demon from Doom 3 is named "Bull Demon"
 * Most of the weapons in the mod come with original designs that resemble combinations of weapons throughout the series, such as the assault rifle from Doom 3 containing the micro missile mod from Doom (2016) or the Unmaker from Doom 64 being merged with the Reaper from Doom (2016)'s multiplayer DLC, Hell Followed.
 * When standing close to the Pain Element or even its variants, they will begin to bite the player, which will affect a strategy that was used to prevent these enemies from spawning Lost Souls.

Source
https://forum.zdoom.org/viewtopic.php?t=53010