Cliffhanger Prepper Stash
You'll want to bring an anti-helicopter weapon with you for this one.
Check out the smashed blue pickup at the base of the Ozhigwan Falls, in the west mountains of Jacob's patch, west and slightly south of the Visitor Center.
The prepper note is right next to the prone victim. Read it to begin the mission.
Your goal is to trace the survivor's path up the waterfall.
Follow the blood trail to the blue-roped ledges.
An enemy helo will close in as you climb.
Take it out, then follow the blue ropes up. At the top, you'll face two ordinary cultists on the south side of the falls.
Just past them is the ex-survivor, and his key.
Open the longbox back at the wreck to complete the mission.