The Dark Lynx Guards the South West part of the Mountain Territory. You will need to Feed him in order to pass and be able to clear in that territory. He will then give you a reward every 12 hours.
There are 2 stages to feeding the Dark Lynx. The reward time is 2 hours for the regular Lynx, and 12 hours for the Dark Lynx. However, the Dark Lynx gives greater rewards!
Don’t forget to craft ahead and be prepared to pay in food each time you visit the Mountain!
Note that Stage 2 refers to the Dark Lynx as a bear. Once you feed it though, it still completes and he lets you pass.