The Chitauri

In the Avengers movie, the Chitauri are an alien race led by Thanos, and negotiated with Loki the Tesseract in exchange of an army to conquer Earth. Loki uses doctor Selvig to build a machine to open a portal in New York with the Tesseract from where the army came. Most of them where killed when Iron Man nuked their main ship, having an apparent vital connection with it. Apparently, they have no morphing abilities. Kleiser is one of the Chitauri's high commanders in the Ultimate Marvel universe.

In Ultima, the Chitauri are designed and characterized much like their movie counterparts, but they are led by Kleiser, as in the comics, with Loki being their army general. Like their movie counterparts, they cannot shapeshift, but they are as clever as their comic counterparts and are constantly scheming different ways on how to take over the Universe. The Chitauri are currently some of the many soldiers in the Organization's Army. Queen Veranke, Malice, and the Super Skrull are the only Chitauri/Skrulls in existence who retain their original shapeshifting abilities, and even they have difficulty keeping those forms for long due to Maleficent's influence.