Board Thread:Game Help/@comment-26965273-20150906235751/@comment-27067797-20151011233540

Hi Bill Cipher618816, The Crimson key mould is a 0.04%  (1:2500)  drop chance from monsters in the Underground Crimson. It is extremly rare to get the key mould, It took me a few hours a day to obtain it.

I recommend that you use a Battle potion and a water candle (obtained from dungeon) to increase spawn rate of monsters in the underground Crimson.

Keep trying and you will eventually get it  :)