On the surface Mount Kadar and the region surrounding it is a frozen wasteland that is almost impassible, partly under the COG's orders, while underground there is a massive tunnel that leads to a large underground river. As well as the massive city and capital of the entire Locust Horde.
Before the Human-Locust WarEdit
Mount Kadar was the location Dr. Niles Samson was ordered to take a number of his test subjects sometime during the research program and the New Hope Research Facility. The COG forbid the use of vehicles and cut off all the roads, and Niles mentions in a recording that everyone traveling would be doing so on foot at night through the snow. It was not known what happened to the test subjects, but Niles's AI remarked of the trip that something terrible awaited them inside the mountain. It is also unknown what became of Niles Samson after he left for this venture though his test subjects, the children of the Sires, eventually became the Locust.
On the SurfaceEdit
During Operation: Hollow Storm, Delta Squad travelled to the mountain region following intel found at the New Hope Research Facility in an endeavor to find a way to the Locust stronghold. Upon reaching the outskirts of the mountain, Delta discovered the entire area was occupied by the Locust and various outposts were set up along the deserted roads. Delta proceeded to fight their way through Drones, Boomers, and Reavers along the roads and across frozen lakes. As they ascended the mountain, they continued to fight Reavers and Seeders, but eventually reached a canyon, which they had to cross by jumping because the bridge was destroyed.
Delta continued travelling up the mountain until they reached a heavily guarded outpost at the mouth of a large cave. After fighting through the outpost, Delta entered the cave and began travelling down.
Beneath the SurfaceEdit
Under the mountain, Delta Squad traveled through a long tunnel, fighting off Corpsers and Brumaks until they found Chaps, who informed them that Stranded had moved underground because the surface was too dangerous. He tells them that how to reach the Locust highway past an underground river, which would lead them to the capital, and recognizes Maria Santiago when shown a picture, but informs him that she was in Stu's group, which was captured. Dom and Marcus continue onward, fighting off Theron Guards and Locust Gunboats, eventually managing to defeat the Leviathan in order to make it to the Locust Highway.