Information and picture courtesy of Genolas.
Location at +1170, +805.
You say, 'Hail, Scout Bristlethorp'
Scout Bristlethorp says 'It looks like you've already done your fair share of adventuring down here in these caves! If you like, you are welcome to relive the tragic Invasion or defend the caves from the foul creatures while you play the role of a [1].'
The task begins in Snarlstone Dens.
More information needed.