a blinking S in a circle

Recently i was waking near Berglum when i saw an S inside a circle, and the whole thing was glowing. I have no idea what to do, what it means, or if its good or bad. Could someone help me?

"I think TV remotes should have a button that allows you to kill the person on screen."-George Carlin

If you have the Pathfinding skill this symbol means there's a secret passage nect to it. Try walking through the trees next to the s.