The return of the Stained Glass Egg

The return of the Stained Glass Egg it's an egg in Mainland.
How to find it: The information of this egg is unknown. Only tucann knows the truth about this one. But there are some things related to the egg:

There is a cave next to the waterfall. And you have to do some steps to get in (nothing could be discovered about the steps yet).

Undertiago64 discovered more or less what is inside the cave. And it was filtered that there is a person to speak inside the cave.