Tain was a sentient bioship created by the Makers.
Tain broke free of Maker control and destroyed its communication organ. It tried to integrate itself into the surface of Espero to prevent the Makers or their enemies the Oon from taking it back to war. Tain also created the night beasts to protect itself. Tain was attacked by Reo, who implanted his consciousness into Tain. With the help of the Eighth Doctor, Tain escaped his body and entered the body of a mokey called Nessus. The Doctor destroyed Tain's old body and Reo at the same time. (PROSE: Halflife)