Please note that the map, below, incorporates both maps used for this mission, merged into one. The reason for this is because the used portion of the first map is very small, and, when put together with the second, what to do in the mission becomes much more clear.
All map locations given from the first map will relate to the specially created one but will have the in-game coordinates succeeding it in italics.
For reference, the two maps singularly can be found here and here.
It is strongly recommended that every member be /THF and/or have radar. The radar will show the position of the NPC Lamiae with a green dot.
Even though the Lamiae are NPCs which show up on radar, they do not show up on widescan.
You start off in the room at (D-9)/(H-6) and need to get onto the second portion of the map at (F-9)/(J-6).
Along the way you will encounter various Lamiae in various places, the first of which roams around the south side of the (E-8)/(I-5) pillar and must always be avoided on the way out.
All the Lamia guards are True Sight and will give a message if they saw you.
If a guard gets within a 5' distance you're captured and sent back to the start point.
Assuming you weren't ambushed and have your wits about you, it is very easy to outrun and lose aggro, even without enhanced movement speed. Running around pillars is a very effective way to shake them. Since the Lamiae never actually hit you, Sprinter's Shoes is an effective item to use here.
The bridge switches are located at (F-8), (H-6), (J-8) and (H-10) as denoted on the map, below. They can be hit in any order, at any time.
Once all the switches are activated the Rune of Release spawns at (H-8).
Be warned that it can be quite tricky to get to due to all the Lamia around it. It may be a good idea to have someone train them away if you're short on time.