Cause of ascian calamity and rejoining elemental

[Anonymoose]

1.what is cause of ascian civilzation calamity that nearly break world

We have no idea! All we know is that there was a "sound" and the "laws of nature" were unmade and the Ancients lost control of their creation magicks.

What is 13 elemental of rejoining that not yet reveal

If I remember the cutscene correctly:

[0] The Thirteenth is destroyed when Igeyorhm accidentally triggers a Flood of Darkness (no element)
[1] The Fifth was Rejoined in a Wind Calamity
[2] The Twelfth was Rejoined in a Lightning Calamity
[3] The Second was Rejoined in a Fire Calamity
[4] The Third was Rejoined in an Earth Calamity
[5] The Sixth was Rejoined in an Ice Calamity
[6] The Tenth was Rejoined in a Water Calamity
[7] The Seventh was Rejoined in a Calamity of all elements tilted towards the astral charge (by Darkness)

In Shadowbringers, we learn that the First was almost Rejoined in a Calamity of all elements tilted towards the umbral charge (by Light).

What will come next (if anything) is unknown. We have gone all the way around the Elemental Wheel and both polarities, so in theory we are done. Why did history follow this very familiar pattern? We don't know! Elidibus seems dedicated to killing the Warrior of Light before he tries any more plans. If we put a stop to him first, we may never see another!

if you can tell me where thats revealed

They probably got the info from a combination of Lore Book 1 (which reveals that Bahamut's calamity was "all elements charged astrally") and Urianger's 5.0 presentation (which revealed that Light is behind the passive charge, what Eorzea would call umbral, ergo Bahamut's calamity - the active astral charge - was elements skewed by the effect of Darkness). In the Exarch's presentation, this Calamity was a color I can only describe as "evil dragonfruit", but it fits, lol.