Teenage Mutant Ninja Turtles x Justice League Turbo is an independent, fan-made fighting game developed by Kamekaze (aka OldEra) in the IKEMEN fighting game engine, acting as an updated re-release of the original TMNTxJL. Being a crossover between Teenage Mutant Ninja Turtles: Tournament Fighters and Justice League Task Force, the game combines these two titanic properties into a single competitive fighting game package, deliberately designed to be a throwback to the most beloved fighting games of the 16-bit era, with simple controls, a cast of fan-favorite characters with lots of powerful tools at their disposal, and a fast match pace with a heavy emphasis on good old-fashioned footsies, as well as a few unique mechanics of its own, all to provide an experience that will be familiar to fans of the fighting games of yore, but with just enough new features to keep things fresh and interesting.
This game takes place during the ending of Justice League Task Force in which a defeated Darkseid escapes to another dimension in search of the Anti-Life equation in which he would use it to dominate any and all universes. Upon learning it is in the dimension he escapes to he makes it his sole mission to find it there. However the very dimension he finds himself in is a parallel universe in which he and all others are seen as comic book characters and nothing more. Meanwhile, Despero found the opening in space time and used it to track down the Justice League for his own purposes. This very place is populated by the Teenage Mutant Ninja Turtles. In search of the equation Darkseid immediately begins reducing entire regions to ash and his very presence causes the world to change. A new power source has revealed itself due to this cosmic imbalance and every living thing is affected by it. It was later referred to as the "Omega Factor". The omega factor, also known as the omega effect began to manifest itself in all people in different ways depending on the amount of hatred in their hearts. Because of this the world began to fall into chaos over time. As Darkseid began his search for the Anti-life equation he felt a huge amount of hatred in an abandoned missile silo. There he found a very dead Shredder. He resurrected him which gave him massive amounts of power and gave Darkseid a powerful enforcer to deal with anyone who got in his way. When he read his mind he learned just who Shredder hated and permitted him to exact his revenge before joining him.
Back at the Turtle's hideout, Donatello's monitor alerted him that a huge amount of activity was detected at the very place they defeated shredder a year ago. When they arrived they found a barely coherent shredder and a dead Karai behind him. They tried to fight him but was swiftly defeated one by one. When it appeared that it was all over, a familiar face appeared to help them escape. Raphael immediately recognized him as Batman and was finally able to prove that they did meet and that he is real. Batman explained the situation to them back at their hideout and they began to search for the other Justice League members hoping they were also transported to this dimension. After a lengthy search they began dealing with the chaos the Omega Effect was bringing to most of the planet as best they could. Eventually superman noticed a huge amount of lava pluming from the pacific ocean and was able to identify that Darkseid was there. The final plan to take him out was established and they split up to initiate it.
The plan went well and it appeared Darkseid was on the ropes, but he revealed to them that he found exactly what he was looking for and tapping into that gave him even more power as he branded himself "Darkseid Omega" ruler of all existence. A combined effort by the heroes and unlikely anti-heroes were able to subdue him before he became too powerful. They then noticed the rift in space was beginning to close and they made preparations to get the Justice League and their dimensional affiliates back home. As they said their final good byes, the turtles and company couldn't help but notice a new series of planets that was a cosmic result of the entire affair setting up the events of TMNT Tournament Fighters for the Sega Genesis.