Hongsil's Secret Storehouse its my favourite event, it's so easy to get rewards on it. I have 13 chars... and i can enter to storehouse 1 at day each one + 1 key each day if you are premium, so thats 98 entries in total this week. That is a lot of exp, mats and event tokens for me. We can get rewarded with keys.. it's just a suggestion that maybe can help.
Thanks for your help!