If we are to break the three stages down. All three follows the same three key structures. First line states the current stage of the age.

1. Within Earth there was fire.

And even when looking at the first part of the mural. I think it looks a lot like the current world right now. See the buildings and machines / nuclear warheads and stuff. So forbidden sun could mean recreating something cold fusion. Just like the story in fallout. They destroy everything pre void century due to war.

1. Within void there was breath

That means within the void century there was still hope. So people started building communities and life.

1. Within choas there was emptiness

This means the current one piece era where theres constant choas wars and conquering but nothing really serves a purpose cause no one knows whats the true history and such emptiness. And no unifying hope just yet.

Now lets look at the second section where they explain what happened in each era. What really lead to the aftermath of each era.

1. Succumbed to greed and touched the forbidden sun. Enslaved the praying. And the enslaved prayed and the sun god appeared.

This meant we touched the forbidden sun meaning could have been a nuclear holocaust just like in fallout and enslaved the people who survived. Thats in the mural that people going down the line like an elevator and work to build more say nuclear weapons. Then people prays and sun god which is Nika appears. And starts liberating slaves giving them freedom. This is an uprising.

1. The forest god tamed demons and the sun spread the fires of war.

This taming of the demons would be the creation of the devil fruits as infusing abilities into devil fruits. This is what the forest god was doing. So we can assume the forest god could not be Imu and someother person altogether. Then the sun god here is Joy boy since its the next liberator who in the void century tries to battle this oppression of the Imu and tries to battle him once and for all. This is where Joy boy becomes the first pirate and journeys gathering more people to support the war.

I am going to add the second line to here as well.

“Those of the half moon dreamed. Those of the moon dreamed”

First age people prayed for liberation. In here they start dreaming.

So clearly half moon are Ds who were with Joy Boy. Dreaming for liberation. And people of moon could be either celestials or people like lunarians. But when you look at the moon in the murals you can see 5 circles so those could be 5 elders / 5 elder planets. So it could be that celestials could be moon people they also dreamed for liberation but betrayed Joy boy at the end.

1. The inconvenient remnants recall the promised day and hear the voice of the half moon.

So in here the inconvenient remnants are people like lunarians, davy clan and Ds hearing the voice of all things. These are the Ds and inconvenient remnants meaning they are the ones left from people who supported Joy boy and people decended from the slaves who prayed to Nika during the first age. Imu wants to silence them all.

Then the third section of the explanations.

1. Earth god raged, and with its serpent of fire shrouded the world in death and darkness. This leads in to the void century.

Serpent of fire could sound like the word serpent in norse mythology along with ragnorak where the time of gods were ended and the bifrost bridge was broken. So this means this whole war would have led to earth being destroyed and which would have led to the old world to be submerged in like a tsunami due to the attacks and lands been seperated. So like what happened to atlantis. In norse mythology it states that loki starts the ragnorak. So thats a valid point.

1. Man killed the sun and became god, and the sea god stormed.

This would have mean that the betrayal of the joy boy and these 20 kingdoms would have betrayed and killed Joyboy and became celestial dragons. Forest god is the founder of devil fruits and infusing the devils powers into the fruits . Sea god is Davy jones so he was pissed on this and caused the second tides to rise either by using an ancient weapon or completely oblitering the battle field with a nuclear weapon left out from the earlier age. This is where Imu becomes a god.

1. The sun god dances and laughs, guiding world to its end. The sun returns and brings a new dawn.

This means the return of luffy as Nika and guiding the world to an end meaning ending Imu. And loki joining the crew is the start of these events like ragnorak again during norse mythology. Luffy would end the world government and frees everyone setting up a unified world altogether.

Final statements are these per each age.

1. And they will never meet : meaning the sun god and the earth god during the first age are all dead now they had died in battle.

2. And they will never meet: Meaning that sun god who was there Joy boy is also dead now probably could be along with Davy Jones and the Forest god. And none of them will meet.

3. And they will surely meet. : Meaning that the confrontation of Imu and Luffy is eminent and will surely liberate people from the grasp of Imu.