Given scene/plot descriptions from movies or TV shows, and given a specific question about the scene, summarize the question into a title

In Supernatural S08E12 AKA As Time Goes By it was mentioned that Abaddon was a hired gun in the series, was it ever revealed who hired Abaddon? Larry Ganem described Abaddon as a "hired gun" in "As Time Goes By".
Who hired Abaddon?