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Zixlyr was an Ice Warrior prince and the successor to his twin sister, Alixlyr as Ambassador of the Martian Empire to Peladon after Alixlyr went missing.

A month after Alixlyr's disappearance, Zixlyr went looking for her. Carrying a Xanthoid volataliser on board his ship, he used an explosive to cripple the ship and make it crash on Peladon, avoiding his cargo being checked. He set off a distress beacon for help, and the TARDIS materialised on board. As the Fifth Doctor, Peri and Erimem reached the bridge, part of the hull broke off, with the TARDIS inside. Zixlyr used the cover story that he had been attacked by Arcturans.

The Doctor, Peri and Erimem helped Zixlyr safely crash land the ship as it entered Peladon's atmosphere, crashing it into a forest. Zixlyr and Peri went to the citadel of Peladon, while Erimem took care of the Doctor as he recovered. Inside the citadel, Zixlyr found Alixlyr's last message on her memory hub, which warned not to trust the royal family and that something dark was at work in the citadel. Peri explained to Zixlyr that this didn't mean the royal family was responsible.

Later, after learning of the truth, Peri rushed to Zixlyr, telling him that Alixlyr did die, but not at the hands of a Peladonian royal. She had been killed by the Osiran, Sekhmet, and had her blood drained to break her blood lock. Inside Sekhmet's tomb, Erimem offered her blood to Sekhmet, but had poisoned it with mandrake root that was inside her ring. Zixlyr grabbed onto Sekhmet and set the countdown on his volataliser. Zixlyr sealed the chamber, blowing himself up along with Sekhmet. (AUDIO: The Bride of Peladon)