Director Kenneth Branagh just revealed the Destroyer at Marvel's Comic-Con booth. Check out the photos of the enemy Thor faces in the upcoming movie.
The Destroyer is an enchanted suit of armor forged by Odin, and when it first appeared it was hinted that the Destroyer had been created as a weapon to face some dark menace from the stars. It is first seen residing in the Temple of darkness in Asia. The Destroyer is used by Thor's arch-foe Loki on several occasions, and each time has actually come close to killing Thor.