Quest to Kill the Ender Dragon is an Xbox 360 series in which Stampy and iBallisticSquid try to defeat the Ender Dragon. This series lasted for 24 episodes and still is a series, only renamed the Quest Series and again renamed the Quest To Kill The Wither.
This series focuses on Stampy and Squid trying to defeat the Ender Dragon. It lasted for 24 episodes.
After the series, they decided to keep the series, and will rename it the Quest series, which is a sandbox series like Stampy's Lovely World. This series are focused on silly things and building pixel art that can be convertible onto buildings.
On January 2015, the Quest series was renamed into Quest To Kill The Wither, as their focus right now is to defeat the Wither, similar to when they try to defeat the ender dragon.