It is rare that a Greevil is blessed, or cursed, with such curiosity that would cause it to seek to enter the Ultimyr Academy, study place of the Warlock. It is an even rarer event that one succeeds.

However, drawn by the unnatural magics within the Greevil found itself upon the Black Grimoire, an ancient spell book of demonic energy. As Greevil's are often, stupidly, known to do it attempted to absorb the magics within. But, the Gimoire took hold and the raw demonic magics flooded into the Greevil's mind.

Twisted, corrupted and bloated on magics from the Demon Realm, the Greevil, now dubbed "Mog'ra the Devourer", serves as a source of untapped dark energies for the Warlock.

(Zoom the GIF for proper resolution, tried some GifCam here to show the swinging motion)