Diablo 4 Lost Cause is a gather quest in which you must help Erdener, a Zakarum Crusader, by collecting Prayer Amulets from cultists near Vyeresz.
Lost Cause is one of the many Hawezar side-quests, and assuming you want to achieve 100% completion in the swampy region, you must finish it.
However, the quest has a pretty tricky requirement you need to meet in order to play it.
In fact, the requirement might cause you more problems than the quest itself.
But no worries because, as always, we got your back, and throughout the following walkthrough, weβll provide all the instructions you need to complete D4 Lost Cause side-quest.
How To Start Lost Cause Quest in Diablo 4
The first thing you need to worry about if you want to tackle the Lost Cause side-quest is to reach the Hawezar region in Act 5.
Then, you must clear the Vyeresz Stronghold, which is found on the south side of the region, north of the Toxic Fens area.
As with all Strongholds in D4, Vyeresz can be difficult to take, but weβre sure youβll eventually succeed.
When youβre ready, head to Vyeresz, preferably using the Waypoint you unlocked by clearing the Stronghold, and talk to Erdener.
The quest giver is located on the west side of the Stronghold, as you can see on the map below.

The NPC will tell you how some personal effects, Prayer Amulets, of the dead Crusaders were pillaged by cultists.
Since Erdenerβs priority is the remaining garrison, he turns to you to collect the Zakarum Prayer Amulets.
As such, letβs see where you can find the Amulets.
Where To Find the Zakarum Prayer Amulets in Diablo 4
After finishing your conversation with Erdener, you should open your map to see the questβs search area in the western part of the Toxic Fens area.

Considering the search area is next to the Stronghold, it shouldnβt take you too much time to reach it.
Once youβre there, start slaying the cultists, which get marked with red dots on the minimap when you get close enough.
It would be best if you would run around the area to gather the cultists into bigger groups and kill them with AoE abilities.

Note that you can run into Elites enemies, and they will be harder to kill, of course.
Also, itβs good to know that you should get a Zakarum Prayer Amulet after you kill about three cultists.
When youβve collected a total of ten Amulets, return to Erdener and give him the good news.
The Zakarum Crusader will be pleased with your work, and youβll get rewarded with Gold, XP, Renown points, and a Cache. Now that youβve completed Diablo 4 Lost Cause, you can turn your attention to other Hawezar side-quests, like Left Behind, also available in Vyeresz.