Underworld Space rising at Night

From the beliefs of Visayan folks.

Earth has dual sphere, the real world and the supernatural underworld sphere.
The two where of the same diameter
It was like  an ocean that rises and fall due to gravitational effect
This underworld sphere also rises and fall.
When night came, it rises above the real world and as it rises, the underworld inhabitants also rises with the bubble and roam the real world freely.
Oftentimes they came to interacts with real world's  inhabitants.
Thus we saw supernatural occurrence.
As the darkness came to an end the risen bubble slowly settles down and sunk under the Earth. In the process it also bring down the creatures that goes with its rising.

Thus a children of the Visayan Island Group were warned by their elders, not to go out when darkness fell for supernatural entity  rises with the bubble sphere at night.