Kelzen was part of a Sensopath trinity. Her other two segments were Jirenal and Shanstra.

After being exiled from the far future, Kelzen's mind possessed Tilusha Meswani's unborn child. Once born, the baby boy Sanjay grew immediately to adolescence and changed into Kelzen. The Seventh Doctor convinced her to let him take the Sensopath away from Earth to prevent her from causing more problems.

Kelzen eventually realised that Shanstra wanted to become the dominant personality once the trinity reunited. Not wanting this, she distracted Shanstra through their mental link, allowing her to be killed by Livewire. Due to their connection, Jirenal and Kelzen died as well. Sanjay was released from the Sensopath's control and decided to stay at the Pridka Dream Centre to explore what he could now do. (PROSE: Infinite Requiem)

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