Marceline, Bubblegum, Finn, and Jake all go to confront the Vampire King, resulting in a pretty one-sided fight.
The Vampire King attempts to talk with Marceline and have some common ground but Marceline only wants to kill him. Eventually she gives up and they end up having a conversation, resulting in one of my favorite lines in all of adventure time.
The Vampire King convinces Bubblegum to remove his vampiric essence and turn him back into a mortal and she agrees to help to Marceline's disdain.
After having his vampire essence put into a bucket and sealed to be buried because it’s extremely powerful. Peppermint butler, after having his vision messed up by bright light, drops the bucket and releases VK’s vampire essence, creating a giant cloud and vampire essence causing destruction and chaos around Ooo.