Mod Endless Biomes by MadoctheHadoc

This biome is based around resistance/strength. Everything from the leaves to the moss to the wood is tougher than normal; if you plan on getting of the wood from these tall forests, you'll need an axe to mine it, in fact it is also often quicker to strip the tough outer layer of the stem blocks and then mine it to get the wood. Some of the leaves glow, mine them to get endurians which give short bursts of resistance when eaten.

The vines in this biome spawn as rows disks dropping down from the leaf canopy with occasional bright bulbs on the end. When broken, these disks slowly float down and drop their throwable item form while the bulbs drop resistive grease which is a crafting ingredient used in a few recipes. There is a new mob in this biome too, the flying, armoured anklor which has a soft upper-belly meaning you need to attack it from above to damage it, use it's drops to craft anklor shell plates and from that craft the disks into a new frisbee weapon (If you have any rifitite shards in your inventory, one will automatically be consumed to teleport your frisbee back to you when it lands) and smith iron into a new set of armour which makes you lighter (so you jump higher). A lot of recipes and stuff I haven't mentioned here so JEI is definitely recommended.

Also you can craft penumbral disks with TNT and resistive grease to make frisboom disks (explosive projectiles)!

This biome is based around radioactivity (weird I know), it's a biome inspired by Australia's Purnululu national park with iceburg-esque "bungles" made of arkan (a new secondary stone block found commonly in the End). Around the central belts of the bungles, you'll find bright pink radon blocks which damage you as you get close. They damage you more as you get closer but thankfully, all arkan derived blocks will block the radiation, more specifically there has to be a straight line of sight between the centre of the player and the centre of the radon block for it to damage you.

Arkan is the block the new Bulwark structure is made of; the structure has two new summonable golem-like mobs called sentinels made from arkan and provides interesting rewards like an item which can teleport you out of the void and a chestplate enchantment like thorns but it teleports enemies away. Radon sentinels are healed by nearby radon blocks and have their own radon attack if they don't hit you for 3 seconds.

A lot of people like the idea of an upside down biome in the End, it would be appropriately strange and leads to some interesting and fun gameplay but to me, upside down isn't enough, the twisted reef has plants which grow in every direction. The biome itself is based around teleportation with big floaty cubes made of coral that go all the way to y = 255. The higher you climb in the biome, the more likely you'll find riftite crystals and shiftling mobs.

Shiftlings are small, shrill, neutral and curious creatures which teleport entities when they attack them so be careful, high up on the cramped little islands, shiftlings can easily teleport you off the edge. The riftite shards dropped from the riftite crystals allow you to teleport vertically upwards on use certainly useful for navigation. It can also be used to craft a few different types of blocks, to teleport entities like shiftlings can (hold it in your hand when you attack) and can be fed to shiftlings. This biome might be made of coral but it reacts pretty negatively to water...

The Overworld has villagers, the Nether has piglins and now the End has it own unique trading system too: Ruinous Altars.

Rather than trading items, you 'sacrifice' yourself to a Ruinous Altar which spawn on various 'podiums' throughout the End. After sacrificing yourself, you get one of six special debuffs (for 15 to 30 minutes) called hexes and some unique items in exchange, this (can) include a new weapon, armour piece and enchantment. Hexes can't be fully removed with milk, instead drinking it will half the remaining time of the effect. This is important as you cannot sacrifice yourself while you still have a hex; transporting a cow to the End could be a good idea for this very reason but just exploring the dimension and being able to get some items every so often is also not a bad idea.

As well as this, one hex called the 'Hex of Truth', allows you to find concentrated void blocks which spawn throughout the End. Bottling these and drinking them allows you to switch between the Overworld and the End from anywhere in either dimension and crafting them with shattered obsidian (another item you get from the Ruinous altar) and radon into an End Altar basically creates an expensive but permanent teleportation platform/anchor. Switching dimension using either an End Altar or bottled void will automatically teleport you to a nearby End Altar on the other side if there is one nearby.

Other small ruins of past civilisations spawn throughout the End.