A Terracor in the Haunted Mansion.

A big brute monster you encounter in various Chapters throughout the game. It's weak point is on his head. When you hit it there it starts rolling around the place like a huge pinball.

You fight one on the Bandits' Warehouse and two in the Haunted Mansion. You also must fight one in the last room of Round 3 at the Arena.

The best way to defeat one is usually to Vertical Slash at its head, which results in you stabbing your sword into the weak spot. This isn't possible the first time you fight one, so you must use Slash by hiding behind the railings. They are one of the hardest bosses in New Game Plus as they never leave their targets alone until they fall (and the huge level boost the bosses earn in NG+ doesn't help either).

Element: Darkness (weak against Light).