Speak to the Captain of Daytower to begin this quest going. He’ll tell you about the journey to Meridian and how it’s not as easy as it used to be. Ask any questions you want of him then follow the waypoint through the wilderness to Meridian, it’s highly advisable you grab a mount for this journey as it’ll be tedious without it. Once you get to Meridian, head up to the guard at the gates and talk to him to start the conversation and cutscene where Erend will show up.
When you’re back in control, follow him to Olin’s house and let yourself in. Use your Focus to investigate the floor to the left of where you come in to discover a trapdoor. Investigate further and you’ll pull it back to discover that you can’t open it with any weapon you have on you. Not to worry, there is another way. Head upstairs, then look for a ladder at the back of the room. Climb up and head around to the end where there will be a pallette with a bunch of metal ingots stacked up. Push them over the edge to break the hatch and get inside.
Head downstairs until you reach the basement room. Use your Focus to scan the datapoint, the map and Olin’s journal, then investigate all 3 to get a full picture of why he lead the Cult to the Nora village. Speak to Erend about it, then head for the excavation that Olin’s map indicated he’d be at. When you get near the site there will be a couple of pairs of Cultists patrolling. Take them out then climb up into the site and move to your marker to start a cutscene. When it’s over, you’ve got to kill a bunch of Cultists and two Corrupters, not an easy task.
The Corrupters are easily the most dangerous thing here, and so they should be your focus. Stay up on the ridge and lay down a bunch of tripwires and traps, then try to pull just one of the Corrupters up onto the ledge with you and onto the traps. If that fails, Corrupters are weak to fire, so either use a Sling or Fire arrows to make it overheat, then hit the weakpoint that exposes itself for big damage.
If that fails, Ropecasting them and then critical hitting or hitting with Blast sling ammo is another valid option. Olin will join the fight when it all kicks off, so he should keep the majority of the Cultists off of you until you down the two Corrupters. When the Machines are down, use your Focus to scan and tag the remaining humans, then mop them up.
When they’re down, go talk to Olin. Decide his fate, although if you do let him live he can help you on the sidequest to save his family. When the conversation is over, that’s this quest complete. Also, there’s an Ancient Vessel here in an Ancient Debris Pile, make sure you snag it!