Verra dimension doors through the wall of ectoplasm before unleashing two rapid strikes, which both hit the unblinded creature (49 damage). All three of the enemy slowly approach Darian and Zelestine. Zelestine strikes the unblinded foe (18 damage), and Darian hits it with a burst of missles (10 damage).
Qataria and Groknar launch attacks at the wall separating them from the others, to no avail. Bellus makes the dead undead even more dead.
I'm going to assume you repeat the same tactics, since your opponents are slow and blinded.
The rest of the battle is brief and predictable. Verra drops the seeing undead with his next arrow, and further injures one of the blind ones. Despite his blindness, the wounded creature gets a lucky hit on Darian (critical, 24 damage). Zelestine and Darian hit it with sword and magic before it falls to another of Verra's arrows. Zelestine is scratched by the final enemy (12 damage) before it is taken down by a final round of attacks (3 arrows, 2 sword blows, and a burst of magic missles).
Several minutes later the walls of ectoplasm fall, freeing the trapped fighters. Investigating the rooms, Verra finds a sealed urn in the rock dust of the northern chamber (contents 350pp, five deep green spinel gems, and a third eye. Bellus locates a secret door behind the alcove on the south wall of the hallway.
Current damage by my count: Darian 25, Verra 6, Bellus 18, Groknar 22, Qataria 47. Zelestine will heal herself.