Fiend mutagen is an alchemy ingredient and is used to craft fiend 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. The earliest opportunity to get this mutagen is during the quest Return to Crookback Bog, where the final enemy is a fiend. All other fiends in the game are of much higher levels.
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.
- A level 16 fiend can be farmed south of Crookback Bog, though there are many endregas and an arachas on the way to it.