I got idea how to improve creativity of the mysterious cave exploration: How about add in the wish credit system to the mysterious cave? like every 50 times the cave key use, guaranteed will get the lvl 4 or lvl 5 runes? either lvl 4 or 5 is fine, just randomly based on RNG dropping of lvl 4 or 5 rune, for that even with the free cave key draw is count towards the 50 cave key. that will make this system more F2P-based event.

the 50 wish credit was for open suggestion, it can be more than that.