One of the most annoying challenges in the game but luckily the achievement tied to it is pretty simple.
First off you'll want to glide across to a section of ladder on the cone in the starting area, which you can see in the video. Climb up, drop down and talk to Hunter.
To get the achievement, follow Hunter and stand over the vents which he waits at, or grab the crystal in mid-air before he snatches it. You'll want to do this on the first part of the challenge, the second would be much harder due to how fast he grabs the crystal.