He had been kidnapping young Martians from the refugee camp on Peladon while trying to find the Princess, but had accidentally killed a mother that was protecting herself. He tried covering up the murder by placing a stolen Pel sabre in her. While Lord Axlaar was defending himself against Grun, Sslurn shot Grun with a sonic disruptor, accidentally revealing themselves in the plot.
The Third Doctor, knowing where the Princess was, took King Peladon, Axlaar and Sslurn to the chamber of the Prisoner of Peladon. As the doors opened and the Doctor asked the Princess to come out, Axlaar threatened the Princess. Before he could fire, the Doctor hit Axlaar in the chest, causing him to fall back and blast Sslurn with his disruptor. (AUDIO: The Prisoner of Peladon)