The Chimney
Took me alot of tries because I got stuck on the middle platform. If enemies were hard to kill prior to the Chimney, then grab some upgrades. Healing wont matter much here. Default healing is fine.
Simply run and be alert, so kill & dodge when needed.
Eventually you’ll get to a middle platform where the crystal cant move. Those roots have glowing yellow pods that need to be shot.
Once at the bottom floor. The crystal will get suck again. Shoot those roots then grab the crystal for the reward.
There might be atleast two elite mobs at the bottom as well so be cautious.
I had trouble with it at first as well, honestly just try and shoot out as many crystals as you can before triggering the device. and try to not spend to much time on clearing mobs than needed. you can evade most of them. only really time i had to worry about the mobs was on the final part when the summoner starts to turn them all into bombs. concussion shot or challenger archtype are nice for clearing big hordes. i think when i did it i had only upgraded my gun once.
Also the device stops dropping when you reach the point where you have to shoot the roots, so use that moment if needed to restock on ammo using the re-spawning mobs and catch your breath.