The extra arms and armor piece came from the video game Asura's Wraith(Which is one of my favorite video games)
Ref- http://www.furaffinity.net/view/17005840/

Fact about the form: Ultimate Titan Fury can spawn the extra arms or us them in energy attacks and blast cause being made of pure energy. If he has no energy arms Crono can use the spots on his back to perform boosts or to spawn another one