|The following information is from the Adventure Time comic book series.|
It may not be part of the same canon or continuity as the animated series.
The Ghost Destroyers are a group of ghost hunters consisting of Anti-Ghost Princess, Cherry Chris and Hairy Chris.
After Clarence abandoned her and all the other ghosts in the 50th Dead World mistreated her, Ghost Princess dragged herself back to life, redubbed herself as "Anti-Ghost Princess" and began to wage a war against the ghosts in Ooo. After becoming an expert in ghost capturing, she recruited Cherry Chris and Hairy Chris and formed the Ghost Destroyers. They proceeded to capture ghosts and put them in a boring and smelly containment unit.
When Finn and Jake turned themselves into ghosts and accidentally scared Princess Bubblegum, she called the Ghost Destroyers to get rid of them. They capture Jake but Finn damages their capture apparatus freeing all the ghosts in containment. Princess Bubblegum activates the "Omega Protocol," which turns the entire Candy Kingdom into ghosts which form together into a giant Princess Bubblegum that puts all the rogue ghosts back in the containment unit. After Princess Bubblegum turns everyone back to normal, Anti-Ghost Princess is still a ghost. She believes this is so she can make amends and help ghosts (because out of all the ghost that escaped about only three ghosts acted like jerks) and redubs herself again as "Auntie Ghost Princess" and decides to help ghosts trying to get into Dead World.