Canon Background
https://awoiaf.westeros.org/index.php/Ballabar

In-Campaign
During Robert’s Rebellion Balabar acted as the gaoler for Maester Thaddeus after Thad was apprehended in a failed effort to turn House Redwyne against their liege and their king. Believing that Thad has violated his vows in his role as an intelligence agent Balabar seeks to extradite him to the Citadel for inquisition and “corrections” from the Conclave.

After Lord Paxter ruled that Maester Thaddeus needed to be found guilty of treason for extradition a trial was held in which Balabar acted as a witness against his colleague. Despite Balabar’s well-reasoned testament Thaddeus was found innocent and released after inconsistent testimony from Desmond and Meatball.