Douglas Hill 
Deathwing Over Veynaa 

It was a sight he had seen once before in reality, and a thousand times since in nightmare. A planet surrounded by a glowing, pulsating, golden nimbus of lethal radiation…Co ninuing his search for the evil Galactic Warlord, Keill Randor, the Last Legionary, joins a rebellion on the Cluster and meets a powerful mutant who may be part of Deathwing, the Warlord’s deadly army.Keill and Glr, his alien friend, must fight this enemy and escape the lethal forces ranged against them. But can they also save the planet Veynaa from total annihilation?