Mojang has released a snapshot of the upcoming Minecraft Nether update. The snapshot is basically a test version of the upcoming update, and you need to enable the snapshot in the Minecraft launcher menu.

So what is in this snapshot? The centerpiece is three new Nether biomes: the Crimson Forest, the Soul Sand Valley, and the Warped Forest. There is also a new high-level material called Netherlight, which is refined from the Ancient Debris found deep underground in the Nether. Netherlight has several useful effects, one of which is that items infused with Netherlight are essentially immune to the effects of lava.

One would expect this from Hoglin, but apparently this new creature "can't do much yet."

Full details of the snapshot are available here, with more information about the new biome. Using snapshots can break worlds, so Mojang recommends backing up your world (or running snapshots in a separate folder) if you want to participate in snapshots.

For a history of what has been added to Minecraft recently, see the Minecraft Update Log.