Zs'Skayr

Zs'Skayr (pronounced Zuh Scare,) also known as Ghostfreak was the Ectonurite High Ecto-Lord of Anur Phaetos and Anur Transyl, and the main antagonist of the original series, Ben 10, season 3. He was originally stuck in the form of Ghostfreak, but after time managed to gain control over it and escape the Omnitrix, becoming one of Ben Tennyson's most dangerous enemies.