Mrrct'llz was a Brv'cllnz. At one point in the 2140s, he was an ambassador to the planet Delcanto. While there, he and two other ambassadors were executed by one of the factions in the planet's civil war.
Mrrct'llz, being an energy creature, was trapped in the film that was made of the executions. Whenever the film was played, he had to relive his death.
Centuries later, Bernice Summerfield and Irving Braxiatel found the film. They removed and destroyed the portion of it that contained Mrrct'llz' execution, at his request. (PROSE: The Light that Never Dies)