I have gathered a little more information about Lord Admiral Loknar (the leader you get after defeating the Guardian). Here are his stats:
Loknar the Last Orion
Starting Exp: 1000
Fighter Pilot* +45
Galactic Lore* +45
Free Techs: Graviton Beams, Nuclear Drive.
When you defeat the guardian and you have room for another leader, Loknar will join you. You will get Graviton Beams and Nuclear Drive (everyone already has Nuclear Drive). If you dont have room for him then you still will get his ship.
When you receive Loknars ship (you will get this even if you don't get Loknar), you will receive 4 Xenon Level Techs. Death ray will be one of them and there will be 3 others chosen at random from the list below:
Black Hole Generator
It will try to choose technology that you do not already have.