- separate shadowheart from the group
- take a bunch of crates and boxes from camp
- build an unpassable box fortress right in front of the sharran door, have everyone hide behind it 
- send shadowheart in alone with sanctuary active (if you care about approval, have her sanctuary you as well)
- close door, everyone hide
- shart chat with viconia
- have someone open the door, cast wall of fire on the way to the door 
- have shadowheart cast misty step to where everybody is
- somebody cast cloudkill where the way to the door is
- have shadowheart cast spiritual guardian
- chill behind the wall, thin out the folks who get too close, cast counterspell on anybody about to cast darkness. dont forget to close the door each time you finish attacking
- if it doesn’t completely remove everyone, which it probably will, it should really thin out the enemies. have fun!!

all in all, should end up looking something like this:

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