You enter a cave in the sumeru desert to shield yourself from the sandstorm outside. After going deeper you can hear something that sounds a bit like.. breathing or a heartbeat. And soon, you hear a loud, powerful voice echoing: "I am Apep, the great dendro dragon. Who are you to think that you can invade my domain?" You can not see Apep, but the voice was addressed to you and certainly not a hallucination.