Also asked, what do I do with extra mutagens Witcher 3?
The mutagens can be placed in the grid to boost abilities in the character screen. Red for sword stuff, blue for spell stuff and green for the poison stuff.
Also Know, what do I do with Wraith mutagens? Wraith mutagens are used to craft Wraith decoctions. They act like lesser green mutagens when placed in the diamond-shaped slots in the character panel.
Also Know, can I break down mutagens Witcher 3?
You cannot break down Mutagens - you have to find them on monsters, and craft them through Lesser -> Regular -> Greater.
Should I dismantle all mutagens?
They can be used to create certain Decoctions and since some monsters only appear once or twice in the game you probably shouldn't get rid of all of them. Breaking them down in the lab is the only reason to keep them.