Murranus was a gladiator. The Seventh Doctor and Mel Bush met him in Pompeii and played dice with him. The dice he used were loaded, but when called out, he accused the Doctor of cheating instead and attempted to kill him, but was thwarted by an earthquake caused by the volcano. He enlisted Valeria Hedone to drug the Doctor, and then he took him to the amphitheatre where he hoped to kill him.
After Valeria arrived to assist the Doctor and the two of them escaped, Murannus and his gladiators remained within the amphitheatre as the volcano erupted. (AUDIO: The Fires of Vulcan)