Among the mysteries not yet revealed in OP is the ginormous creatures to one of whom there was interaction with, Zunisha.
These creatures could actually be the protectors of Kingdoms on the surface in Ancient Times and likely controlled and commanded by Uranus.
Just like how Poseidon commands SeaKings and we could call them protectors of The Oceans the same way the Gigantic creatures above waters could likely br protectors of Land, and actually commanded by Uranus the Brat
The gigantic creatures we know as of now are
1: Zunisha the Protector MokomoDukedom
2: The Gigantic Shadows above sea during Thriller Bark
3: and Finally the Gigantic Skeleton's Skull in Onigashima who very likely is one of these creatures and the Sword next to its Skull is its weapon and very likely it is/was protector of Wano
these two countries are known to be on side of Ancient civilization and so very likely the gigantic creatures were also on Ancient Civilization's side, as their guardians
These creatures could actually be the protectors of Kingdoms on the surface in Ancient Times and likely controlled and commanded by Uranus.
Just like how Poseidon commands SeaKings and we could call them protectors of The Oceans the same way the Gigantic creatures above waters could likely br protectors of Land, and actually commanded by Uranus the Brat
The gigantic creatures we know as of now are
1: Zunisha the Protector MokomoDukedom
2: The Gigantic Shadows above sea during Thriller Bark
3: and Finally the Gigantic Skeleton's Skull in Onigashima who very likely is one of these creatures and the Sword next to its Skull is its weapon and very likely it is/was protector of Wano
these two countries are known to be on side of Ancient civilization and so very likely the gigantic creatures were also on Ancient Civilization's side, as their guardians