The Kraang are multi-tentacled brain-creatures who came to Earth a millenia ago from another dimension to colonize it. Unfortunately for them, the Earth’s biosphere is not particularly hospitable to them, so they’re plotting to transform the Earth’s environment into something more suitable for their own kind – and destroy all human life! They brought the Mutagen Ooze with them from their own dimension, but it doesn't work as they thought it would. Kraang Prime is their leader.