This mystery can be found in the east of Suthsexe, about 630m east of Cicestre Abbey.
How to Complete Fly Agaric in Suthsexe
As Fly Agaric mysteries go, this is a relatively simple one. All you have to do is defeat the Jotnar shape-shifters which appear as soon as you eat the mushrooms. You’ll be fighting a bear, three wolves, and a lynx. The bear will transform into a Jotnar-Guld if you give it enough time, and the wolves and lynx into regular Jotnar troops. The Jotnar-Guld has superior range and strength, and will initiate more special attacks than the others, but that’s about it.
Once all the Jotnar / animals are dead, the mystery will complete.