Depths (Disambiguation)

The Depths is a subregion of the Subterranean region that is important to the Plot. There is no threat of rain.

The Depths (Spoilers ahead)
The Depths are a seemingly abandoned series of temples and shrines. You must have a certain symbol to get here. Strange, tall beings can be seen, with four arms and many legs. They project strange images similar to the ones that Five Pebbles projects when the slugcat enters. The creatures appear to be knitting things with their hands(?) Throughout the Depths, the final symbol is seen on buildings and statues. As you go deeper, the world gradually takes on a golden hue, ghostly slug things appear and things seem to go underwater, with everything becoming wavy. Very uncomfortable. When you reach the very bottom, everything becomes gold and black. Spirits head towards the water at the bottom-most point of the entire world, where a watery substance (the Void Sea, according to Big sister Moon) covers it. From here, the only place you can go is down. As you are going down, eventually the Void Worm examines the slugcat, hooks it onto a string and drags you down even farther at frightening speeds. When it lets you go, no golden light is there and everything except the slugcat is black. At this point, swimming is the only thing you can do (your breath now has no limit). As you swim, other slugcat, or maybe copies of the original slugcat begin swimming with you. Swimming to the light triggers an ending cutscene and earns the achievement Ascension.