Signature exclamation of
Thundarr the Barbarian, one of
Jack Kirby's coolest creations and the best reason to get up on
Saturday morning in the
early 80's.
We have to assume that the Lords in question are Thundarr's primitive gods, but AFAIK, they were never explored in more detail in the series.
Along with Ookla! Ariel! Ride!, Lords of Light! is also code for "I am a geek" when used in mixed company. Other geeks may take the exclamation as an invitation to discuss cartoons and comics, King Kirby, Gamma World, or breakfast cereals.