There are a few level 4 (or so) skeletons, several crates/barrels and a few chests (with ok stuff, but nothing special).
Even if you get the seekers sent on a punitive mission, the next time you see them (fighting a troll near Lovis' tower) if you are fast enough to talk to Merrill before they die, you can still get the quest, unlocking the hatch (presumably an oversight in the dialog system).