Prerequisite: After visiting Aya and landing on Voeld.
As you approach Techiix, you’ll get a comm message asking you to help him find a cloaked wraith in the marked area of the frozen lake. You have to use the scanner to find it, somewhere in a bunch of rocks within the marked area. After scanning it, the mystery sniper will take it down exceptionally.
Head to the marked location to find the sniper named Orev. Talk to him and ask him about joining the resistance. If you have Jaal with you, he’ll easily convince Orev to talk to his father about letting him join the resistance. Once done, the task will be complete.