Vaatika, the Cryptic Caverns

Beneath the world's southernmost continent as part of the Underworld is the Vaatika, also known as the Cryptic Caverns, a set of eerily geometric caverns, filled with myriad plants, animals, and environs that are strangely distinct from one another. Arid sands, frigid tundra, and verdant forests knit together like puzzle pieces. Though ringed by small settlements, the deeper caverns are uninhabitable, with the deepest chambers formed entirely from metal and filled with eerie runes.

Flora and Fauna
The flora and fauna of the Vaatika changes across its caverns. Some chambers contain evergreen boreal forests, while others might hold a vast expanse of desert cacti with the appropriate beasts for the climate. All across the Cryptic Caverns, within its odd geometric halls, goats of otherwise unremarkable appearance are reported to appear from the walls themselves, only to be preyed upon by strange hairy creatures, with red eyes and a great wingspan. In a region bordering the "normal" outside reaches of the Vaatika and its inner geometric halls, lies a forest most uncanny. Though it has never been seen to move, every few days all plant-life in the area changes place, giving it its most usual name - the Shifting Forest.

In the umbral depths of the Cryptic Caverns, travelers have reported seeing dark slender shapes out of the corner of their eyes, watching them from the shadows.

Lizard-Leeches(?)

Yeti
Little is known regarding the Yeti tribes that live and hunt upon the edges of the Shifting Forest. Though they aid the occasional travelers they encounter heading in and out of the woods, they largely keep to themselves save when trading the few 'safe' plants and animals they are able to procure from deeper in the caverns.

While largely peaceful, they have seen enough tragedies arise from dangerous animals and plants being taken from deeper in the caverns without proper handling, and so these secretive hunters often shut their doors to travelers they feel too irresponsible, and on rare occasions even take up arms against them.

Kappa
Living at the furthermost edges of Vaatika, the kappa settlements were originally founded by travelers from Zhanyi that became trapped within the winding passages of the underworld, and sought refuge from the frigid cold at the edges of Vaatika. Though a passage back to Zhanyi was mapped after many years, the path proved to be long and difficult, and so many of the travelers opted to remain in their new settlement at the edge of the caverns, studying the curious plants and animals within, and interacting with the rare, but strange explorers that occasionally seek to enter the caverns.