Would these gamers be old enough to remember the 80s cartoons? You could set it up as a plot by the older ponies (maybe the one with the jewel-eyes?) to re-assert power. Bonus plot point: iirc, there was a pony named Rainbow Dash in the original. Is the monk a sleeper agent?

Ready-made villains: a trio of bumbling witches, a bunch of evil bee-folk...