Hedin was a member of the High Council of the Time Lords.
Biography
Out of sympathy for Omega's plight, Hedin helped carry out Omega's plan to bond with the Fifth Doctor and achieve physical existence once more. He shot Talor with an impulse laser, allowing him to remove the records of Omega's theft of information from the Matrix.
Hedin was also an old friend of the Doctor. When the Castellan attempted to kill the Doctor to prevent the bond from taking place, Hedin sacrificed his life to save the Doctor, allowing Omega to complete the bonding. (TV: Arc of Infinity)