Tetsu-Oni

The Utrom known thus far only as Tetsu-Oni or the Iron Demon, was an ally of Takeshi Tatsuo and the Kitsune. It provided the Foot Clan with Utromium, one of the components required for mutagen. It was this substance that kept Tatsuo alive for many years longer than he should have been.

Many years later, Oroku Saki, who harbored the spirit of the now-deceased Takeshi Tatsuo, had the Iron Demon summoned only to attack it, and destroy the portal from whence it came.

Trivia

 * Tetsu-Oni (鉄鬼) does loosely translate to Iron Demon. However, the Oni were a specific sort of demon - large and ogre-like in appearance.
 * The robot body is an obvious homage to that of Krang's in the original animated series.