Mutagen is a substance obtained from the bodies of mutants and armored hounds. Despite being called a "mutagen", this ingredient is not used in any of the mutagenic potions. It is also one of the least common ingredients in the game. There is a possibility of finding some in Act I, if Geralt chose to fight the frightener in the Prologue, but otherwise this item is not found until Act V.
Source[]
Notes[]
- Special ingredients are also referred to as "mutagens". These ingredients are entirely unrelated to the mutagen described above and are required to make mutagenic potions.