You say that there are not enough diamond keys, but you can get them by collecting 60 million points in diamond events, or if you are too lazy to collect that much, you can buy them for gold. Let's say I never bought diamond keys in a shop, but at the same time I had 56-odd diamond keys, I had to spend them because there was boring. Diamond characters are expensive to upgrade, so getting the keys should also be difficult. This game, by the way, is a free game and there is a donation store for players to spend money on resources. Actually, I play without donation and for some reason I have enough of these elemental essences, I don’t even have anywhere to put them.