So I have recently come back from taking a break for a long while. I have caught up the MSQ up to defeating the Warriors of Darkness (which I just did a few mins ago).

Can someone clear up the concept of worlds and such for me cause I am having a hard time wrapping my head around it.

This is my understanding:

Hydaelyn and Zodiark once existed in Harmony until Zodiark decided he wanted more

Hydaelyn sealed Zodiark up in the moon (or what I assume to be a moon given the whole "lunar body" thing")

This action caused the "Source" (which is...something?) To be split into thirteen worlds.

Ascians seek to destroy the worlds to cause the pieces to return to the Source and make Zodiark whole, and have done so seven times.

Now here is my confusion

What is a world exactly? Is it like another planet? Another dimension/plane of existence?

What is the Source exactly? I thought it was Hydaelyn at first but it seems to be something different.

When the Ascians cause a rejoining it appears they destroy a world in doing so, it is also said that this is marked by calamities of the Umbral eras. However Eorzia is not destroyed by the Umbral...it suffers them and moves onto astral eras until the next one. Is this a case where when one world is destroyed all the others feel its effect in this Umbral Era's?

The first world (the one the warriors of darkness said is being destroyed by light)...what exactly...happened? I know that they have said it is being consumed by light and thus being destroyed but what caused it to be consumed by light (were they just defeating too many asicans?) and what do they mean turning into a void?