Before joining the Inquisition, Threnn served with Loghain Mac Tir's forces at Ostagar during the Fifth Blight. She has expressed a view of Loghain's innocence, and believes that King Cailan over-extended his forces and the signal fire was lit too late by the Warden and Alistair. Threnn escaped with the rest of Loghain's forces.
If Anora remains queen of Ferelden and is ruling alone or alongside Alistair, Threnn will state that Anora took pity on her because of Threnn's loyalty to Loghain, Anora's father, and so sent her to either help or hinder the Inquisition, depending on the World State.If Alistair was made king of Ferelden and rules alone or alongside the Warden, Threnn will state that he sent her to the Inquisition to simply get rid of her.
Threnn serves as the quartermaster for the Inquisition and is in charge of the requisitions.
During the assault of Haven, Threnn is seen fighting either Red Templar or Venatori forces. If the Herald fails to help her, she will fall. If she survives, she joins the rest of the Inquisition in Skyhold, though she no longer serves as the quartermaster. She can be found walking around in various locations. Eustace Morris takes on the quartermaster role, and says it was thought best Threnn be replaced with someone more politically palatable, now they are in Orlais.
If Loghain was made a Grey Warden she will comment on going to give him her respects when he comes to Skyhold, and the fact that he even remembered her name. She reiterates that he was "the best commanding officer this world has ever seen."