Zhaan is Delvian, species known for their religiousness. She is very sensual and likes to meditate naked. Her blood is very valuable.

Pre-Farscape

 
Zhaan and her lover Pa'u Bitaal lived a peaceful life on Delvia, planet ruled by theocracy. Pa'u Bitaal was a powerful member of the ruling faction. When the day came for them to be replaced, Pa'u Bitaal and the rest of his faction refused. Instead, they hired Peacekeepers to help them "keep order" and stated killing everyone who protested. Zhaan's father was among the ones captured and sent to a forced labor camp. She was betrayed by the man she trusted the most. She killed Bitaal while they were sharing the Unity. As a consequence, her own mind was broken.
 
She spent next 10 years in prison, serving her sentence first in Mekkar 7 labor camps, then on Moya. One day, during her incarceration on Moya, she had a vision prompting her to join the Seek. She healed her mind using meditation and other Seek techniques. Through effort she eventually became a ninth level Pa'u.
 

Farscape TV series

 

On  the crew, Zhaan was the voice of reason and he knowledge of species biology often came handy. However, her dark side sometimes revealed itself - Zhaan was among the crew members who wanted to trade one of Pilots arms for a star chart, and during crew's encounter with evil Maldis, Zhaan was forced to use the dark in herself in order to defeat him. The worst blow came from Pa'u Tahleen, who entered the Unity with Zhaan solely to learn how to overpower her dark impulses and not go crazy after hurting others. Tahleen refused to let go and broke Zhaan's mind again. She was saved by John Crichton who entered the Unity with her, even though he risked his own life in process.
 
Zhaan decided to stop being priestess in the wake of these incidents. However, she was forced to take a mantle again in order to defeat Maldis again. Kahaynu, one of the Leviathan Builders, enabled her to hear Moya's thoughts, and after that she dedicated herself again to protecting both Pilot and Moya.
 
Stark and Zhaan formed a relationship during his travels with the crew. 
 

 Zhaan's death

 
After restoring dying Aeryn Sun to life Zhaan was very weak. This weakness caused her to contract a fatal decease. However, there was a cure - a suitable planet would do the trick. Even though the rest of the crew was looking for the way to cure her, Zhaan resigned to her destiny and accepted her death. During their search for a planet that could cure Zhaan, John Crichton gets distracted by a wormhole that suddenly appears. Moya is diverted from the previous course in order for them to investigate wormhole. She collides with another ship in a freak accident, and Zhaan is forced to sacrifice herself in order to save the rest of the crew.