This weekly quest becomes available at rank 10 with Prey: Season 1. The weekly quest can be completed once, on each of your max level alts, which is useful for both farming Remnant of Anguish, as well as completing the achievements for defeating every prey target on every difficulty level. If you choose a Nightmare difficulty hunt as your weekly customized prey hunt, completion awards 150 Remnants of Anguish. At the Hard difficulty level, only 120 Remnants of Anguish are awarded upon completion. Normal hunts give 90 Remnants of Anguish.
IN ADDITION, there is also an unlisted reward of 25 Hero Dawncrests for completing this on Nightmare difficulty. The quest rewards only lists Champion Dawncrests, but you somehow get both the Champion Dawncrests as well as the hidden Hero Dawncrests. Unclear if it's a bug or intended.
Edited for May 12, 2026 hotfixes: This quest is now infinitely repeatable, but with reduced rewards after the 1st completion for the week on any toon on your account. If you are only interested in the achievements for defeating every prey target on every difficulty level, this will be a great change for you! If you were enjoying the easy 25 Hero Dawncrests on every alt, this will not be a great change for you. The quest now only gives 5 Hero Dawncrests per completion, subsequent to your account's first completion of this quest per week.