Nukus
A creation of Les Fortunes, the overlord of the second dimension. Hid away in Art Fortune's vault until the Magnavores took the picture and Vexor brought him to life. Nukus quickly set a plan to dispose the Magnavores and took over as the new villain. He broke Les out of jail to use the artist's skills to create lethal monsters that could be brought to life with the use of his sword. He had an advantage over the Beetleborgs as he destroyed both the paper he came out of and the copy Art Fortunes owned. Nukus is the one who destroyed all of the original Beetleborgs' powers and arsenal. He later gained a Mega form, Mega Nukus, from touching Les Fortunes' transmographier device which he destroyed soon after to ensure no one else received a upgrade from it.
Horribelle
Second in command of the Crustaceans, an insect-based sword-toting fighter and Nukus' right-hand woman. Like Nukus, she can summon a face-mask in battle. She also wields two swords that resemble mantis arms. She once rebelled against the Crustaceans by having Les Fortunes create the Astral Axe, so she could control its' powers out of a scorn for not receiving a mega form like the main male villains.
Vilor
Third in command of the Crustaceans, a fish-based, trident-toting fighter. He briefly gains a second form, Super Vilor, when the Mantrons arrived, and later a brief Mega form, Mega Vilor, after touching Les Fortunes' transmographier device prior to its destruction, though he somehow reverted back to his normal state.
Lester "Les" Fortunes
The black sheep in the Fortunes family, Art's younger brother. He was in jail when Nukus broke him out to his cause. Despite creating all the Crustacean monsters and their arsenal, Les never gets any respect or credit for it. At the end of the series, he goes back to jail for some peace and quiet.
Worm Tanks
Giant worm-like vehicles summoned to attack the Beetleborgs.
Crustaceans Jet Fighters
Air-borne machines summoned to attack the Beetleborgs on several occasions.
Mantrons
Evil counterparts of the Astralborgs called Scorpix, Centipix, Mantix, and Hornix. Created by Les Fortunes as a child to rival Art Fortunes' Astralborgs in their only collaboration, the Lost Comic. They were there to aid Nukus in his plans to get Roboborg, who ultimately made it to the good hands of the Beetleborgs. In 'Roboborg' (part 8 of the Lost Comic saga), the Mantrons were finally sent back to the Lost Comic for good by the combined attacks of the Beetleborgs, Astralborgs and Roboborg.