Nightwraith mutagen is an alchemy ingredient and is used to craft nightwraith decoction. They act like lesser green mutagens when placed in the diamond-shaped slots in the character panel.
Like all special mutagens they can only be dropped by their corresponding monster, but this mutagen is also a guaranteed drop from any nightwraith. Additionally, any regular noonwraith can be swapped by its counterpart at night, so one can pretty much choose any such target. However, all are higher level than Jenny o' the Woods, so it's easiest to just do her quest.
Notes[]
- In an undocumented change for Patch 1.08, all mutagen icons were changed. However, there was still a bug for those on Steam and Origin that didn't reflect this and was later fixed in Patch 1.22. Despite this, some may still see the original icons instead, even with a fully patched game.