What I did was head around the side entrance/above entrance to the complex (look upriver at the main bridge before the ruined temple, hint hint) and bust through a cracked wall as quietly as possible; it brings you inside, above the goblin shamaness's 'throne room'.
Watch out! Their vision is broken and they can still see you as soon as you move across the beams.
What I did was take my warlock with misty step and split him off from the group, got as close as I could, and teleported across; it began combat with him. I dashed on my turn, as the ai didn't seem to consider moving to the second way up until after I had passed it, and dropped down into the goblin shamaness's private quarters and lockpicked the door to the underground.
After that I just snuck around the ogre guard, still just with my warlock, picked the locked lever to avoid the puzzle ( or do the puzzle if your perception fails, or save-scum till you get it) and headed into the underdark.
There are no enemies in the ruined temple, so it's a free run to the waypoint; at which point you can select one of your other characters, hit 'm' and just teleport them to the waypoint.
There you go! You can easily rp it as someone scouting ahead and clearing the way, because that's exactly what it was. Good luck!
PS: If you decide to go this route, settle in for a half hour/45 mins or so of play to do so, as there are about 10ish enemies that will trigger when combat starts. By far the most tedious portion of what I did was just the dashing and waiting for everything to take its turn.
Last edited by Mister Monster; 12/10/20 03:54 AM. Reason: Edited with 'PS'