Thalen was a Xindi-Primate engineer assisting Degra in building the Xindi superweapon. He was Degra's friend and chief confidant.

In 2154, Thalen assisted Degra in testing the second prototype of the Xindi superweapon in the Calindra system. Their work was interrupted when the Andorian warship Kumari stole the prototype, which was later destroyed by Captain Archer. (ENT: "Proving Ground") Shortly thereafter, Thalen was captured along with Degra by Archer and the crew of Enterprise to gain information as to the whereabouts of the superweapon. His memory was erased by Phlox so he would not remember the incident, or that Degra had unknowingly revealed the location of the superweapon. (ENT: "Stratagem")

Later, in February of 2154, as Degra's shuttle returned to Azati Prime, Thalen shared a toast with Degra over the near-completion of the weapon. (ENT: "Azati Prime")