This skull once belonged to an adventurer or some other traveler that wasn't quite prepared for their journey and paid the ultimate price for it.
The skull is sentient. Determine its personality and other characteristics using the rules in the "Sentient Magic Items" section in chapter 7 of the Dungeon Master's Guide.
Regardless of its disposition and personality, the skull has detailed knowledge of one or more wilderness locations of the DM's choice. It also has detailed information regarding the circumstances of its death, which occured in one of the aformentioned wilderness locations.