Use “[World Event] <Event name>” or a similar label to notate which events give a bonus chest. This would hopefully happen before the Megadestroyer is added to events that give a bonus chest. Basing bonus chests off of the NPCs instead of the events isn’t very intuitive because the mega world bosses aren’t explicitly labeled either and more focus can be done on tasks that don’t involve DPSing the boss but will still count as participation for the event.