The Aether II is a massive otherworld dimension made up of gigantic sky islands of varying biomes. But in order to get there you’ll need to make a portal of quartz blocks. Then activate it with a bucket of water.
You’ll end up in an Aether outpost, greeted by a man named Edison next to a fire pit. You can chat with him and he’ll explain the Aether to you. These outposts are on each island and are the only way back home. Just click the fire pit if you need to leave.
You can even trade with Edison if you need supplies.
The further you explore you’ll notice that each island has a very steep edge and you may not even see where the next one is. This means you’ll need to work hard to make it to other islands and subsequently other biomes as each one is made up of a single biome.
There’s so much to discover with this new realm that it’s almost an entirely new variation on Minecraft. There are many hidden gems like NPC villages and new foods and tools not to mention various dungeons to loot.