Exiled to a toxic waste dump world reserved for Dimension X's most dangerous criminals, Slash, an eco-terrorist from the planet Palmadise who met and befriended Krang and Bellybomb. They escaped the waste ship and headed for Earth where they fought, and were defeated by the Teenage Mutant Ninja Turtles.
Slash later resurfaced in a state of berserker rage in South America and took a bomb being dropped on him just to render him unconscious. The Mutanimals finds a newspaper about the event and believing Slash to be one of the Ninja Turtles, break him out of his cage. When Slash regained consciousness he attacks the Mutanimals, but is subdued by Leatherhead. The Mutanimals discover that Slash's world was strip-mined and that all he really wanted was to live in a place that reminded him of home where he could live in peace. The Mutanimals bring him to an environmentally protected island, and Slash was finally at peace. That was until the Mutanimals were killed in cold blood by Mr. Null's Gang of Four. Slash, the Ninja Turtles, Ninjara, Future Raph, Future Don, and Master Splinter joined forces to avenge the Mutanimals and stop Null, Maligna, and their henchmen from destroying Earth.
In the end, Slash died when he refused to leave Maligna's hive which was crashing into the sun in order to make sure Maligna and Null didn't escape. The Teenage Mutant Ninja Turtles, Kid Terra, April O'Neil, Oyuki, the future TMNT, Ninjara, Splinter and a couple others held a funeral for him and honored Slash as the fifth Ninja Turtle in a sunset memorial ceremony. It is unclear at this point if Slash will surface in new TMNT comics.
Slash is a snapping turtle that was being used for experiments while in Stockgen. He had been injected with various amounts of mutagen with samples also taken from Old Hob. He grew to adult size but much larger than the TMNT's. His intelligence was very low, and he was known for wild outbursts and rampages until security would appear to stop him. Eventually he would break out of Stockgen and then wander the streets causing destruction and would be given the name "Slash" by the media for leaving slash marks on objects he came across.
Encounter with the Turtles
Slash would soon run into Michelangelo's friend, Woody, and would terribly injure him sending the human to the hospital. Slash caught a glimpse of the Turtles during one of his rampages and decided to follow them to their new lair. Once he made it there, a huge battle began between them with Slash easily over powering them. Slash was able to take everything they could dish out and things looked hopeless for the group. Still, refusing to give up, the Turtles would begin working better as a team taking the fight to Slash and eventually taking him down for a little while; but the Turtle refused to quit using his overwhelming strength to send the group into the air and crashing to the ground, with only Leonardo being conscious.
Slash kicks Leonardo across the room, then proceeds to land the killing blow on an unconscious Michelangelo. Leonardo rises and attempts reasoning with the monster due to not understanding the reason for his attack. Casey Jones and April O' Neil would appear with a flashlight shining it on the combatants. This caused Slash to next tackle Leonardo and the result was Slash being stabbed deep into the shoulder being brought close to death. He stumbles backwards and falls into the sewer. Slash makes it to shore where he's greeted by Old Hob whom was able to sniff Slash out; with a sample of Splinter's mutated blood in his hands, he invites Slash to join him.
Joining Old Hob
At some point, Leonardo is kidnapped by the Foot Clan and Old Hob offers his help to the Turtles hoping to let bygones be bygones. The Turtles are shocked to see Slash is partnered with him, during this time Michelangelo befriends Slash offering candy in which the Turtle enjoys. In their first attempt to save Leonardo, Shredder had already brainwashed the Turtle to fight on his side, and the group are facing certain death until Slash saves them under Hob's orders. The Turtles make another attempt to save Leo when they crash a meeting between Shredder and the gangs of the city. During this time Slash battles against various criminals, and even saves Casey Jones by knocking out Hun with a single blow. They accomplish their goal, escape from the area, and Leonardo thanks Slash by leaving him two gifts: a black bandana and a claw weapon.
Slash along with Old Hob kidnaps a former scientist of Stockgen named Lindsey Baker. Hob wants to create a mutant army and he needs Baker's knowledge on mutagen to do it. She perfects the mutagen and needs a test subject. Slash takes it from her and uses it on himself. He immediately goes into a rage until Hob stops him with a taser. When Slash comes to his senses he displays new intelligence by being able to form coherent sentences and continues to surprise those around him.
Vs. Rocksteady and Bebop
Later, Pigeon Pete mistakenly believes Rocksteady and Bebop to be friends, and brings them to the alleyway Old Hob and the Turtles are having a meeting. To try and stop a fight from happening, Old Hob attempts to reason with Rocksteady and Bebop asking them to join his mutant army, pointing out that Shredder is only using them as slaves. When Rocksteady mentions that they're both half-human, Hob shoots them both immediately and the fight begins. Slash goes after Rocksteady matching him in strength. Next, Rocksteady punches a car towards Michelangelo and Slash takes the massive hit protecting his friend. This permanently removes Slash from the battle, and when he returns Rocksteady and Bebop are defeated.
Slash has demonstrated super-strength, invulnerability, and expertise skills with a katana, bo, sai, and nunchaku. He is adept with every weapon that the TMNT wields, as well as Pantera claws similar to those used by Shredder. Slash is short tempered and has been known to fall into berserker rage, he seems to grow only stronger while in this state and has been depicted of fighting off all four Ninja Turtles.
Slash possesses great strength being able to easily over power the Turtles and constantly fight them back despite their best efforts. He's quite invulnerable being able to withstand melee attacks but he's not indestructible. Originally Slash's intelligence was very low, but after receiving another dose of mutagen; he displays great intelligence not only being able to understand Lindsey Baker's scientific explanations, but easily understands Hob's directions on how to by-pass Donatello's tight security programs.
Teenage Mutant Ninja Turtles (1987 Animated TV Series)
Slash appears in the original Teenage Mutant Ninja Turtles animated series as Bebop and Rocksteady's creation to complete tasks Shredder assigns them that they don't want to do. He is considered to a very strong mutant turtle who is obsessed with trees like in other versions. Bebop and Rocksteady, who exposed Slash to mutagen, one day aggravated him to the point he went berserk, stealing some of Shredder's weaponry and fled to Earth where he played has an enemy of the Ninja Turtles.
Teenage Mutant Ninja Turtles (2014 Animated TV Series)
Slash appears first as Spike, the turtle pet of Raphael. In the episode "Slash and Destroy" (the title of the episode was a homage to the title of his first comic book appearance which was titled "Search and Destroy") Spike mutated into Slash. He later resurfaces as a vigilante fighting the Kraang, and became an ally to the TMNT. The TMNT offer him a place on the team, but he declines, stating that he works better alone, but thanked them for the offer.
Slash appears as a boss in both the NES game Teenage Mutant Ninja Turtles III: The Manhattan Project and in the Super Nintendo version of Teenage Mutant Ninja Turtles IV: Turtles in Time at the end of the prehistoric level, which he is considered one of the games most difficult bosses as he blocks most of the player's attacks.
Compared to other TMNT characters, Slash has had relatively few collectibles released based on him over the years, to date he only has a single action figure by Playmates Toys, a Dress-Up Kit which included a Black Bandana with a turtle "nose" sewn on, a pair of plastic claws, and black "foot clan" knee pads and elbow pads, and a glow in the "pre-mutated" turtle that was included with cans of purple matagen goo.