Lair

A Lair is a part of mineshaft, which is literally below the mineshaft.Lairs are very abundant in ,lapis lazuli, gold, diamond, and redstone ores, and new ores like uranium and onyx.

If you're lucky, you might find a chest in a minecart with the ingot forms of these ores.You might be wondering.., if there are minecarts, then there must be rails right?

YES

In Lairs, you can find long railways, which sometimes go very deep underground, so you might so might find bedrock and deepslate.

Lairs also have these new type of fungus called Glow spores, which glow, and provide light in these dark caves.

There are also mobs which reside in these caves, such as skeleton miners, skeletons with gold pickaxes that will guard their precious findings at any cost.

Other mobs include blind axolotls, cave scorpions, cave spider, atomic creepers, and warden

As you keep going deeper you'll run into a big door, which probably marks the dead end, but you'll find out that if you get your hands on 6 relics of different colors(each crafted by warden horns, and 4 onyx, and one of each dye to provide the color.Once you put all relics in, you'll make your way to battling the cave monster, a gigantic spider-like mob which has 128 hearts(256 health)