What everyone always neglected to mention while explaining the reasons for the Dead King's success in hiding his location was his considerable power.
Orpal was a Divine Beast with a small army of loyal-ish, skilled Awakened who protected him because by doing so they protected their own interests.
On top of that, he was bonded to one of the most powerful relics on Mogar and possessed a mage tower.
Sometimes, wanderers and hunters would get close enough to his fortress, but they would always be spotted long before they noticed anything suspicious.
The Dead King had the means to capture the interlopers, interrogate them to discover their intentions and how they had found him, and stage their demise close enough to their last known position but too far away from his hideout to draw attention to it.
