The Mysterious Key in Far Cry 6 is an item obtained from Yaran Story “Fetch Quest“. It can be used to open a chest that contains the unique weapon “Fuck Anton“.
How to Get Mysterious Key
First you must play the Yaran Stories Who’s a Good Boy? > Fetch Quest. This questline starts in Madrugada region at Montero Farm. See the questline start in image below. During Fetch Quest, Chorizon (little dog) will lead you to the key. It’s mandatory to pick it up, so you can’t miss it. You always get it automatically from that quest.
Where to Use Mysterious Key
The Mysterious Key is used to open a chest in Isla Santuario > Quito > Prado Meadows > Casas Cove > on a small island called “Guau-Guau Island”. It unlocks the unique Rifle “Fuck Anton” (which is one of the 49 unique weapons required for trophy 
Armed to the Teeth (also see All Unique Weapon Locations for the others).
There’s no more use for the Mystery Key after this.
For more tips, secrets, and guides check out the Far Cry 6 – 100% Completion Wiki & Strategy Guide.
Leave a Reply