- Complete Monster: Though this title, originally based on the first cartoon series, started off as a more lighthearted series, that soon changed:
Because death, destruction, these are my favorite things, the things I do best.
- Krang is far darker then the animated version. Working with Shredder to defeat the Turtles, the Turtles' discover the depth of Krang's evil when they fight two aliens named Wingnut and Screwloose. After the Turtles defeat them, Screwloose explains that Krang's forces invaded their home planet of Huanu, killing most of the population. Krang's forces have been going around Dimension X, destroying all life on any planet they find, searching for a powerful crystal called the Turnstone. Another former warlord from Dimension X named Cherubae has possession of the Turnstone and is hiding on Earth. Krang, feeling he needs more powerful allies to defeat the Turtles and Cherubae, contacts the insect queen Maligna. In exchange for loaning him ten of her insect warriors, Krang promises to lead Maligna to Earth, so that her insect warriors can kill the human race and colonize Earth. Krang is ultimately defeated and Cherubae uses the Turnstone to banish him to the prison planet of Morbus. Krang eventually escapes from Morbus and returns to Earth, where he graphs himself on to Shredder's body and plans to kill the Turtles and then hunt down their loved ones, not caring how much damage Shredder's body takes while fighting the Turtles.
- The aforementioned Queen Maligna is the cruel leader of a race of alien insect warriors called the Malignoids. Maligna and her children seek out worlds teeming with life and consume them. Maligna is introduced when Krang contacts her, promising to lead her to Earth, if her warriors defeat the Turtles. After Krang's defeat, Maligna comes to Earth and begins her invasion. She sends eggs to Earth; these eggs contain larva which devour everything in their path. She also sends pods to Earth, containing more adult Malignoids, who will attack everything in sight when they hatch. Maligna also has a habit of eating her own children, devouring one of her Malignoid warriors after he successfully completed a task for her. Maligna captures Raphael and Mondo Gecko, planning to have them fattened and dipped in honey, so she can devour them in a feast later. After the Turtles and their allies defeat her children on Earth, Maligna sends her armada of space ships to destroy everyone on Earth. Maligna is eventually defeated and vows to leave Earth, but later says she will return when they least expect it. Maligna returns much later, after her ally Mr. Null kills the Mighty Mutanimals, removing several of the heroes who opposed her off the board, planning to finish what she started and destroy the human race.
- The aforementioned Mr. Null was introduced as an unseen tycoon, who enslaved a remote South American tribe to work in some of his mines and tries to dump toxic waste into the ocean. However, we soon discover that Null is actually a demon and has sold the Earth to the aforementioned Queen Maligna and her hordes of insectoid aliens, who plan to destroy humanity and colonize Earth. After the Turtles and their allies the Mighty Mutanimals thwart this alien invasion, Null seeks revenge on them. Null takes control of the Horsemen of the Apocalypse and captures the two groups. Null is planning to make the female members of the Mutanimals into his harem, while the others will be slowly electrocuted to death. Null plans to force Kid Terra, one of Null's former underlings who turned against him, into pulling the switch that electrocutes his enemies, wanting to torment his former employee. After this scheme is thwarted, Null later returns and hires some cyborg assassins, who manage to kill most of the Mutanimals. Null decides to torment Candy Fine, who the girlfriend of Mutanimal Mondo Gecko, by showing her images of the Mutanimals burning in hell. Null then mind-controls her and makes her into his slave. Null had the Mutanimals killed so he can continue what he started, trying to help Maligna destroy the human race. When asked why he does what he does, he responds thusly:
- Ensemble Dark Horse: The Future Turtles, especially Don and Raph.
- Hilarious in Hindsight: The comic was easily the darkest book Archie Comics published at the time, which led to several problems with the editorial because of the more adult content. In the 2010s Archie has started publishing several darker titles in order to reach an older audience.
- What Do You Mean, It's for Kids?: Some of the later stories rivaled the Mirage book in terms of grittiness, even though this was the kid-friendly TMNT book. This unfortunately led to problems with the editorial staff at Archie Comics.
- To elaborate: The Mutanimals were brutally shot to death on-panel. Despite time-travel being involved, the team stayed dead. When it was revealed the demon Null was behind it, he disguised himself as one of Candy's deceased friends just to torment her with an image◊ of the Mutanimals burning alive in hell.
- Another storyline had future versions of the TMNT travel to the past, where they met up with Adolf Hitler. They tricked him into committing suicide◊.