World of Cardano
The unknown land
Thandor consists out of two big mountain regions, which are called the "Unknown Mountains" for a reason: No one ever made it out alive, except for its habitants, the Yi'Ras. The Yi'Ras avoid the sunlight and solely live in these massive domains, isolated from other people. Survivors of war describe them to have hyper-sharpened senses, an incredible pain resistance, and an aggressive nature. This is the reason they are feared as deadly foes. It is said that everyone who caught a clear glimpse of a Yi'Ras never spoke again, out of sheer fright.
This makes not only the exploration of the region very hard, but also the communication: The Yi'Ras' only peaceful action in the last century was to prevent attacks on foreign territory. It is believed that these mountains contain many valuable minerals and sediments, but also underground rivers and cavities.