Shadow in the West is a Side Quest in Horizon Forbidden West (HZFW). This walkthrough will guide you through all objectives of the Shadow in the West side mission.
Location: Barren Light
Quest Giver: Conover, but starts automatically after turning in his previous quest Shadow from the Past
Quest Level: Level 10
Requirement: Complete Side Quest “Shadow from the Past”
Reward: 2500 XP, 3 Skill Points + Saved the Daunt Trophy
Mission Info: Eclipse holdouts are gathering in the Forbidden West, rebuilding their army after the Battle of the Alight. They must be stopped for good.
Objectives:
- Go to the Eclipse Hideout Coordinates
- Kill the Eclipse
- Find an entrance to the Eclipse Hideout
- Talk to the Utaru prisoner
- Find Vezreh
- Enter Verzeh’s Chamber
- Kill Vezreh and his Machine
- Investigate Vezreh’s Chamber
- Talk to Yef
Starting Location: Barren Light
Shadow in the West triggers automatically after doing 1 previous Side Quest: Shadow from the Past.
Go to the Eclipse Hideout Coordinates
During the Shadow from the Past side quest you will find out about the leader of the Eclipse and their hideout in the west. Once you complete the before-mentioned side quest, you will automatically get a waypoint to the area south-west of Barren Light.
Kill the Eclipse
Once you reach the area you will have to kill all the enemies and machines in front of the big gate. You can hold 
to see the outline of nearby enemies in yellow. Remember to kill the machines too, not just the humans.
Find an entrance to the Eclipse Hideout / Talk to the Utaru Prisoner
After defeating the enemies, approach the big gate and the Utaru prisoner will shout in your direction. Talk to him and he will tell you about the way into the hideout. You will have to climb the scaffolding he just came down from and navigate around it to enter the compound.
Find Vezreh
Inside the compound kill the enemies. Then enter the ancient door, see the location below.
Inside you will find some prisoners in a cage. Open the cage door to set them free.
Then enter Vezreh’s Chamber to the left.
Enter Vezreh’s Chamber
Inside the Chamber you will find Vezreh who is not happy to see you.
Kill Vezreh and his Machine
Vezreh will call a Ravager to aid him in the fight while he will be shooting at you with a heavy weapon from the podium. Take care of the Ravager first. Then focus on Vezreh. You can hide behind the stone pillars, but they will eventually fall apart when he shoots them too often. His weapon needs to cool down after he shoots for a while. This gives you an opportunity to go for headshots with your bow. Remember you can slow down time and zoom in with while aiming the bow, go for headshots and stay in cover when he shoots. Alternatively, if you have a Spike Thrower it will deal a lot of damage to him.
Investigate Vezreh’s Chamber
After the fight, do not head outside. Stay in the chamber where you spawn. You must use your Focus (hold ) to scan the 3 purple datapoints (logs) in the area.
The first is in front of you to the right of where you spawn after the fight:
The second one requires you to turn around from where you spawn, enter the room behind you.
To the left of the second log is a vent you can pull out with the pullcaster 
+ 
> hold 
. Then crawl through the vent to the room behind it for the 3rd and final datapoint. After scanning all 3 the objective will update to talk to Yef.
Talk to Yef
Finally talk to Yef about your findings, who is standing at the exit of the chamber, where the first datapoint was.
This finishes the Shadow in the West Side Quest in Horizon 2: Forbidden West.
For all other Side Quests and Main Quests, check out the complete Horizon Forbidden West Walkthrough.
Could Not have completed all three games without your excellent, helpful guides.
My only disappointment was the inability to fight underwater as Snapmaws and Burrowers Can and Do attack Aloy, she is unable to fight and must hide or flee.