The New Shredder

The Shredder has been a number of beings. Oroku Saki, Ch'rell the Utrom, Karai, the Tengu Shredder, the Cyber Shredder. All of them one of the most powerful villains of the Turtles have faced. In the comics, even Raphael was the Shredder.

So other characters could be a Shredder. From any of the other Turtles, their allies, their other characters, or even crossover characters. This storyline deals with that new Shredder.