The Krishna Upanishad belongs to the category of Atharvaveda. It describes various incarnations of Lord Krishna in Sanskrit. It not only describes Lord Krishna’s incarnations but also his various Leelas. This Upanishad was written after Lord Krishna’s period.
Krishna Upanishad is a good explanation of Lord Krishna’s incarnations and his relations with friends and family.
The description of Lord Krishna’s physical appearance is quite astonishing in this Upanishad. People of Vaishnav community consider this Upanishad extremely important. They consider it holy and sacred.