Page "Commander Keen" Paragraph 28

Mortimer's main goal is to destroy all beings of lesser intelligence ( i. e. the entire galaxy ).

In the first game series, Mortimer enslaves the Vorticons, a once peaceful alien race, and attempts to use them to destroy Earth.

In the second game series, Mortimer convinced the Shikadi, a race of energy beings, to destroy the galaxy.

Mortimer's next plan was to destroy the entire universe, but as the trilogy called The Universe is Toast was never created, his plans were left on indefinite hiatus.

However, Mortimer had another couple of appearances: he is responsible for Keen's babysitter's abduction in episode 6 of the series, and in the Game Boy Color release of Commander Keen, Mortimer is responsible for another alien race attempting to rule the galaxy.