Krang is the disembodied brain of a Dimension X warlord. He and Drakkus built The Technodrome together.
After being exiled from his home dimension, he teamed up with The Shredder, although in effect he gives Saki the orders.
Krang is partially based on the TMNT comic characters of Utroms. In some continuities, he is an Utrom. The 2012 cartoon, The Kraang are a faction of the Utroms which share a hive mind with Kraang Prime.