This is a custom of Dark Leo from the 'City Fall' story arc. He turns on Splinter and his fellow turtles and joins the Foot Clan as Shredders 2nd in command.
For this custom I heavily modified one of the 5 inch Leonardos with Aves and the red portions are made from ribbon. I wish there was more to the description but that is basically the whole recipe. Just sculpting, ribbon application, gluing a few things on, and then paint.
The figures contained in the Custom Showcase are not for sale by Figure Realm, and the creators of the customs are no way affiliated with Figure Realm. The Custom Showcase is purely for entertainment purposes and only provides a means for the creators to show off their work and trade ideas. Figure Realm does not make or sell customs.