This biome is based around resistance/strength. Everything from the leaves 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 (stripping the tough outer layer of the stem blocks and then mining it is a quicker way to get wood here). 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)!

Occasionally you will see clearings full of Obsidian Boulders too.

Inspired by Australia's Purnululu national park with iceburg-esque "arkan bungles" made of the secondary stone block. Here you'll find bright pink radon blocks which damage you with radiation as you get close. They damage you more as you get closer but thankfully, all arkan derived blocks as well as anklor armor will block the radiation.

Arkan is the block the Bulwark structure is made of; the structure has three summonable golem-like mobs called sentinels and provides interesting rewards like an item which can teleport you out of the void and the vwooping enchantment which teleports enemies away; this is the same ability Riftite Sentinels use while Radon Sentinels use radiation to attack you.

There are many variants of the structure, including the rare Resitive Bulwark with their own Resitive Sentinels, the variants have various challenges and rewards.

The End is weird and this is the weirdest part...

The Twisted Reef is a species of water-hating coral that does not care about gravity growing plants in every direction. The biome itself is based around teleportation and spawns coral islands up to the build limit. The higher you climb in the biome, the more likely you'll find riftite crystals and shiftlings.

The riftite shards dropped from the riftite crystals allow you to teleport vertically upwards on use and are used in various recipes to teleport entities like shiftlings can (hold it in your hand when you attack) and can be fed to shiftlings as well (for which they will kindly teleport you very high up).

Shiftlings are small, 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 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.

One hex, the Hex of Truth, allows you to harvest bottles of void from gusts during void rise weather events. Bottles of void allow 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, these are where the Anklor Upgrade template can be found.