To gain access to Malachite Cavern, speak to the Darkdale Village Elder. He will give you a Village Elder's Trial Note and ask you to bring him 20 Dried Lizards within 30 minutes. If you have the Dried Lizards in your inventory when you take the quest, he will take them out of your inventory and call you a cheater. It's best to collect them ahead of time, put them in your bank, accept the quest then withdraw them.