Last summer I spent 30 days addressing all the canon immigrants in the Teenage Mutant Ninja Turtles world. You wouldn't think an independent comic that doesn't think too highly of most of its adaptations would have many immigrants, but it does - especially since the current IDW run is trying to distill every previous run into something new that all works together. And from what I've seen, they've been doing a pretty good job of it.
Of course, as the series is still running, it can still introduce new canon immigrants, and that brings me to Wyrm!
Wyrm is a mutant that originated as a group of worms that came across a broken canister of mutagen (the same canister as the Turtles? Who can say) and developed a hive mind and the ability to form into a body. You can't quite tell from the picture, but Wyrm is an updated version of this character from Teenage Mutant Ninja Turtles Adventures #10 (May 1990):
This Wyrm is a mutant leech who wants to drain the Turtles of their mutated blood. But it's not so strange that he looks different, because he also looked very different when he became an action figure in 1991:
Of course, the action figure's backstory is different too, as he started out as a garbage man who was mutated into a leech, or worm, or something. He doesn't really look like either one.
Anyway, the yellow one later revealed he could break into individual worms as well, so the IDW Wyrm is following from that. The hive mind is new, though.