Though she appears to be a child, Tressa is actually elderly. Her race's aging process is the reverse of the human aging cycle, so Drayans reaching the end of their lives reach a state of physical and mental immaturity.
In accordance with Drayan funerary customs, Tressa, Corin and Elani were delivered to one of the moons of Drayan II where they would expire. Their journey did not go as planned as the shuttle transporting them crashed and they were left alone until they encountered Voyager crew member Tuvok, who had also crashed on the moon. Tuvok did his best to protect the frightened children, but in the middle of the night, Corin and Elani were drawn towards a cave which was regarded as the Drayans' cradle of life. It was here that they expired and when Tuvok went looking for them, he found only their clothes inside the cave with no trace of any bodies. After the other two children disappeared, Tuvok tried to get Tressa off the moon. The Drayans forced him to land and pursued them, and Tuvok refused to let the Drayans take Tressa. He was shocked when he found out that she was nearly a hundred years old, and that the life cycle of the Drayans were reversed; Tressa had been brought there to die a natural death. Tuvok stayed with her to comfort her in her final moments.