He is a recent top graduate of the Imperial Academy of Coruscant and survived a surprise subversive attack by deep cover Rebel forces. He, along with the Emperor, Darth Vader, and Moff Trachta are en route to the Prism, a fortress that houses Jedi captured prisoners of war.
After arriving to the Prism, Tohm, Vader and Trachta take control of the prison and offer the inmates the opportunity of freedom in exchange of their service in a planned attack to Gentis Rebel forces.
After their attack is succesful and the Rebels are dealt with, Tohm is promoted, but promptly killed by Lord Vader by dropping him from a tall balcony after the Emperor expressed his interest in Tohm as a worthy succesor, if Vader ever fall.