Due to 1.18 generation Custom Overworld biomes need to replace vanilla biomes, i replaced ones that have variants to them that are identical, the names of the biomes replaced are shown so you know where to look
Xeno Wasteland (birch forest)
New mobs: infected animals and hostile mobs

Super-Composted Trees (meadow)
New mobs: Claire the maker of Dreams (trader, passive)

Fall Forest (savanna) 

The Asteroid Residues (Mesa Plateau Stone)
New mobs: Scrap soldier (hostile)

The Acidic Seas (Lukewarm Ocean)
Mobs: Acid rain mobs

Endra Forest (spawns randomly in the outer end islands)
Mobs: Erode (hostile) End Blazes (hostile)

Fusillade Forest (warped forest)
Mobs: Flamelin (hostile unless wearing gold, can be bartered with using warped crystal shards)

Charred Crusts (spawns randomly inside the nether wastes)
Mobs: Brimstone apprentice (hostile) Ally (tamable with brimstone or chaosplate) 3 Headed Ghast (boss)

Depending on the biome you are in you will have a different cave system, here is the following ones you can get

Eidolon Caves (spawns at deepslate under the acidic seas/lukewarm ocean)

Dune Caves (spawn underground in deserts)
 

Dolo Caves (spawns underground in Mesas/badlands)

Mossy Caves (spawns under Supercomposted Trees/Meadows)
 

Frosted Caves (spawns in any frozen biome)

This addon adds lots of different blocks for you to build with all of which can be obtained in survival mode either through crafting or naturally spawning means, some require to be picked up by silk touch in order to take with you

Basic blocks

Plants

Boss Relics (1 in 250 chance drop from any boss, these allow you to summon whatever boss it dropped from infinitely for no cost to the player, ones on top being droped from Superbosses, more on that in the information category)

Pride Flags (can be crafted or bought from a flag dealer for a rainbow gem each, flag dealers spawn naturally in any biome similar to wandering traders)

Stick blocks (these are placable sticks which also can be crafted into armor stands corresponding stick block 
 

Crafting stations (all of which have new recipes for new items like boss summons, armor weapons an more, more information in extra information

Ores
 

The mod comes with a large amount of new materials, weapons, armor and items to just have fun with, some items have special abilities which are told in the description of the item, and if its a different type of item it will show that it is for example if its an item that belongs in your offhand it will say "offhand accessory"

New weapon type Lances (these will provide area of effect damage, range of that area affect varys on the lance you are using, it will show the stats of the area affect including range, damage and cooldown time before you can use area affect again

New weapon type staffs (these provide an attack thats a little less in damage but high in range, some have special mechanics to them other then just shooting projectiles out, projectile damage and cooldown time is shown on the staff)

New swords (most have abilities other then for being in close range situations, either on a close range hit or interacting with the weapon these abilities may save you, cooldown for abilities and ability type shown on the sword)
 

Other weapons, these consist of scythes, hammers, a candle and harps.

Offhand items, these provide buffs when held in your offhand, most are crafted but some are rare drops from bosses and mobs

Crafting materials, probably the most common item type you will have, most are drops or found in chests in structures

Armor,  this addon adds lots of different armor, almost all better then netherite, some provide bonuses when you have the entire set on for example if you have an entire set of brimstone armor you can walk on lava, some are for pure cosmetic sake like slime armor or the cat ears (defense, knockback resistance and armor abilities shown, chestplates show abilities)
 

Tools, most tools mine stuff faster while as some can do amazing things like give rewards when using them or deleting a large number of blocks (brushes shown near the bottom are for mining up rubble of different types more on that in information)

These are changes in the overworld like structures, cool things to find and massive overhauls to the generation, for example going far enough in the sky allows you to see the True Clouds area and going higher you can find Meteors

New mobs: Small Elppa Cube(passive), Big Elppa Cube(passive but like to follow players), Eye (spawns at night, hostile) Reaper (spawns at night, hostile) Halloween spirit (spawns at night, hostile)

Note: every 8 days or on your first night in the mod Acid Rain happens in the acidic seas (lukewarm ocean) shortly after that the blood moon rises adding lots of horror and a new boss that spawns randomly during it called Bloodclops

The True Clouds (spawns at y256 an higher in any biome, going to the acidic seas (lukewarm ocean this area will apear different))

NEW STRUCTURES
Leaf houses (spawns in any form of forest other than the supercomposted trees (meadow))
 

Exo Lab(has a variant depending on the dimension you are in, this is the overworld variant)

Purium Geode (spawns in deepslate and consists of voidstone, moss and purium crystal)

Abandoned Lab and the Abandoned Facility (spawns at -45 an under)

Deep Dark End Portal (spawns in the deep dark and is another way for you to go to the end other then locating the stronghold)

Not many things were added to the nether as i feel the nether has a lot , lots of changes of textures an a few new structures were added though

The Brimstone Church and the Brimstone Helltower as well as some Crystal clusters, all of these which spawns in the nether wastes)

The end has seen a total rework thanks to this mod, new features were added such as new mobs, a new end islands a new area in the sky of the end, new bosses a reworked dragon fight and much more!

The End Spawn

New End Islands

Some New End Structures, all of which spawn on main end islands 
 

The Stars Above (this area spawns at y180 and higher in the end dimension and if the player is in survival this is completely LOCKED until the dragon of corruption (the ender dragon) is killed, going up there will quickly result in instant death if the dragon isnt dead
here are some important places to visit while you are up here

Before playing do /function recommended_settings in chat, this will toggle all settings recommended for a playthrough

Starting with progression, beginning your playthrough is the same as vanilla exept with a few new things, after a while in your new world you may see a message in chat saying Sulfurous Clouds Cover the Acidic Seas which means acid rain is beginning in the acidic seas, this is an event that new mobs and rewards for participating in it, if you are near an acidic seas at the time going there wouldnt be such a bad idea, shortly after that when it becomes night time a blood moon will rise, spawning a bunch of horror like mobs to attack you, the one you want to keep an eye out for is bloodclops, as its a boss that drops an important item called Gore, which is used in the Xenotable (crafted with either 4 Xenomite or 4 infected planks) to make a boss summoner cfor the giant eye. image below shows what all boss summon items look like, not all bosses are crafted  some spawn naturally and those are the following and where they spawn/how they spawn:
Monsoon Witch: Spawns during Acid Rain
Bloodclops: Spawns during Blood Moon
3 Headed Ghast: spawns rarly in the nether wastes
The Brimstone Witch, Calamitas: spawns by using a charred idol crafted in the xenotable at an alter of the witch found in the brimstone helltower
Lord of Gloom: this is the mods reworked wither fight spawn a wither normally to to fight
Draesteel Masterbot: found in the Draesteel monument in the End or can be crafted using the decryption computer at its forth upgrade
The Astral God/The Astral Dragon: spawner can be found by unlocking ascended astral crates found in some stars above islands, astral crate keys can be made in the tyrants forge dropped by the etrnal tyrant)
Brothers of the Cosmos: spawned by throwing a Comit Shard(dropped by the astral god/astral dragon) onto a rematch ritual tile crafted in an astral forge(can either be found in some stars above islands or crafted in a tyrants forge dropped by the eternal tyrant)
Celestial Soul Serpent: spawned by throwing a Metanova Comit Shard(crafted in an astral forge) onto a rematch ritual tile crafted in an astral forge(can either be found in some stars above islands or crafted in a tyrants forge dropped by the eternal tyrant)

SUPERBOSSES
Superbosses have much more powerful abilites then a normal boss and have impacts on the entire world such as debuffing the players in a large area, fire storms and many other abilities, these forms of bosses also have music that play in the background and have a different icon for there boss summoner instead of using a biohazard symbol as there base design for there summoning item as well as having a different color and different 3d model for there boss relics, superbosses will also drop 2 boss bundles which are talked about later. the following bosses are superbosses:
The brimstone Witch, Calamitas
Dragon of Corruption(reworked Ender Dragon)
Astrageldon(lunar version)
Terminus
HATE
Astrageldon(solar version)
The Determined Color God

BOSS BUNDLES
boss bundles are loot bags given out to nearby players of a defeated boss, when opened the player is given items that the boss drops such as materials, weapons armor and some even have legendary items which are more powerful then normal items and are really rare drops, image shown is what boss bundles look like

CRAFTING AND CRAFTING STATIONS
starting off a useful feature in vanilla minecraft is a switch in the crafting table screen, disable that to see everything that is craftable in that station alone, using the search menu may help you glook for what your looking for better when this switch is disabled,  there is a lot of different stations for crafting, all of which have different uses, some are there for saving items, some are there for converting and the rest are there for making brand new equipment for you, the following are crafting stations and are shown how to get and what there purpose is

Xenotable, crafted at the crafting table, purpose is for making equipment and most boss summoning items
Dye Table, crafted in the crafting table. used to dye most dyable items for no cost
Energy Station, crafted in the crafting table or found in the overworld Exo lab, used to make electrical items such as lightsabors
Decryption Computer, has lots of upgrades used to increase items crafted init, upgrades are shown in the tables recipes, all of which require relic shards which are obtained when using a brush to collect relics and throwing said relic on the decryption computer
Extractor, made in the crafting table, purpose is to convert items into different ones allowing you to save resources
Table of infection, crafted in the xenotable or found in an abandoned facility, purpose i an upgrade to the xenotable adding more recipes
Voidforge, crafted in a crafting table, purpose is for making void and dark related items
The Tyrants Forge, dropped by the eternal tyrant, purpose is for midgame crafting items
The Astral Forge, can be crafted in the Tyrants forge or found in some stars above islands, used to make most astral/star related items
Cosmolight Crucible, crafted in the astral forge, used for making most endgame items
Exhume Pentagram, crafted at a cosmolight crucible, used to enchant curtain items with Exhume 
Universe Originator, crafted in a cosmolight crucible, used to make astrageldon related items
Hatred Table, made when a the superboss HATE walks or one of his projectiles hit near a Classic crafting table, purpose is for making hatred related items
 

These are little videos about the addon and what you can see inside the addon and these trailers show how far the addon has come sense it was launched 1 year ago
 

NEW BIOMES!!

Heart of the Community, this biome consists of Basalt, Community Crystal and Ash blocks, this biome had zero new hostile entities and prevents all but bloodmoon hostile entities from spawning

Cherry Grove, this biome like the fall forest is more of an ambient biome thats purpose is to just be explored, this biome allows you to get some cherries for your adventure though so this is a good biome to visit for food

Soul Bloom, this is a sub-biome that spawns commonly inside soul sand vallies, this biome doesnt consist of ?nbsp;much, its just a few soul trees and a soul chest that contains loot related to the soul sand valley

CAVE SYSTEMS

Crystal Caves, these cave systems spawn in specific biome types under y=0, there are 7 different types of them here is images of a few of them

NEW ITEMS AND BLOCKS

New music discs, these can all be crafted from the empty record and a few different items depending on the disc, one disc can be obtained after defeating the Superboss, Calamitas

Colored Flames and dyable flint and steel, these flint and steel will allow dyable fire, all you need is flint and steel and the dye of your choice