Deliver Grelin's report to Senir Whitebeard in Kharanos.
The troggs in the tunnel are extremely hostile, and haven't shown any hesitation in attacking travelers through the tunnel. You seem tough enough, though, so you should probably be safe.
Directions? If you're going to speak with Senir, you'll find him in Kharanos.
Make your way through the tunnel, and after you come out on the other side, just keep following the road, it'll run right into Kharanos.