Take Elynisi to the inn where she will be safe. Other survivors took refuge in a temple on the other side of the bridge.
Inside the temple you meet the Forlorn One, the only spirit not trying to kill you. There is a decanter of holy water in the temple. It might be able to extinguish the magic fire in the Chamber of the Tree. The decanter is in the lower level on a northwestern desk. Use it on the brazier of blue fire, and the echo of Vox appears.
Talk to the Forlorn One again. He shows you a vision of Vox entering the temple. She claims she is going to free the people from the Three.