Credit to reddit poster trueanarchist42. I apologize if it's a repost but I didn't see it on trending and feel that something of this importance would be. Basically the keys will enable you to continue to receive loot rewards from prison of elders even after you've completed the specific activity before the weekly reset. This will be great for people wanting to run again with friends or just your hard core players looking to get as many rewards as quick as possible. You receive 1 key upon completion of prison of elders so these keys are only useful if you are running multiple times in a weekly cycle. EDIT: multiple reports from guardians of keys not dropping for completing the 32/34 POE for their first time. Bring a key if you have one if you are doing this event if you want the big chest until we get clarification if this is a bug or working as intended.