1x7 - Adventure Time - Mini Series “Stakes!”

The group prepare to confront the Vampire King, who unexpectedly appears and says he no longer wishes to be a vampire. He maintains this, despite Marceline's attempts to attack him, and the group reluctantly agree to remove his vampiric essence. Bubblegum uses the same contraption she'd earlier used on Marceline, which turns the Vampire King into a relatively harmless lion, and puts his vampiric essence in a bucket. Bubblegum leaves Peppermint Butler to properly dispose of the essence but he trips, causing the essence to detonate into a new monstrosity: The Dark Cloud.