Apologies I forgot to mention something! The mobs here can drop bells, which when you use them, will spawn a bunch of mobs at your location for you to fight (think star's end tower). What I recommend doing is saving up a bunch of them and then popping them all at once so you can cleave all the mobs down. You'll get a message on your screen essentially saying "The bell's sound can not be heard" when the event is over.
