If you happen to have a shotgun available, it would be a wise decision to bring it along for this mission. If not, then a powerful weapon like a LMG would also be useful.
This mission is given to you by Longinus, who mentions that a helicopter went down over the mountains with a shipment. Talk to the Sherpa and you’ll be transported to the Himalayas. The first thing you’ll notice is that there’s a snowstorm going on, which will be helpful for you, as this limits the enemy’s vision.
Always keep a lookout for enemies, especially since your own vision is somewhat impaired as well. As you head to the first objective point, bear to the right and you should see a lone enemy digging something. Sneak up and use a Takedown on him, likely netting you an oxygen mask in the process, making it easier than getting one from the tent (might have to loot the body).
With your newly acquired oxygen mask, you now have an oxygen meter at the top of your screen. Should it run out, you will eventually suffocate and die. It can be replenished by finding little oxygen canisters, either laying around normally or dropped by enemies.
If you don’t get one from there, then you’ll have to go inside the building, noting there’s a few more enemies hanging around it. Once you have the mask, head towards the next objective, keeping to the right side of the area to possibly avoid getting spotted by the wolves in the area. When you enter the yellow area, your tracker is automatically brought out for you.
The light on the tracker will flash whenever you get closer, and remain steady when you are facing the target. Your target for now is a body and you’ll find a wolf having a meal of it as you get closer. Kill the wolf and then loot the body to find an empty box. Three new objective points now show up on your map, so head towards the eastern one first.
Hug the mountain wall while heading there, stopping whenever you hear two snowmobiles passing. Also, be careful of the enemy patrolling the area. When you get close enough, you’ll find a little encampment with a few enemies, including one on a small ridge overlooking it. Take out that enemy first, then pick off the others, including two more who show up. Loot the marked enemy, then make your way to the next closest objective.
You can follow the ledge from the camp to eventually find a grapple point (before a gap you would need to jump), allowing you to climb up towards the next objective. Be careful here, as there might be some snow leopards and even an eagle flying around. You just need to find another dead body up here, similar to the first one you found, which will yield another empty box.
The last objective marker will lead you to a cave, with something very dangerous inside, a bear. If you have bait, you can toss one to distract while you search for the body containing the shipment. If not, then a shotgun is highly effective in killing the bear. Using the first method will require you to be quick, while you can take your time with the second method.
Find the body, loot it, then exit the cave via the other opening you find, leading you back outside. You now can return to Longinus, which is done by talking to the Sherpa located at the marker. However, there will be more enemies searching the area, so be careful and kill a few of them to help with your oxygen meter. Talk to the Sherpa, who will bring you back to Longinus and the mission will be over.