Tzik'nith is a Lamia who may be found in the Hollow City in Coldharbour. She will only be found in the city if you choose her side over that of the Shadow Walker Wood Elves in the quest Into the Woods.
The final assault to end the Planemeld is at hand. We need to fight our way through Molag Bal's defenses and reach the portal to the planar vortex. Only then can we end this threat and save our world.