How do calamities work, again?

[Hezzlocks]

The Flood of Darkness on the Thirteenth was too much. The other shards rejoined before they were too flooded all the way.
The Flood of Light on the First would also have been too much if Minfilia hadn't interfered back during HW, so Elidibus was probably counting on Urianger getting involved and asking Minfilia for help.

Actually, I don't think he was. The Warriors of Darkness arrived in the Source *while the flood was happening*, but were quite content with toying around with the WoL and taking the long way around to causing a Calamity via aggravating all the Beast tribes into summoning stronger Primals. That is, at least, until the WoL stopped the Garuda summoning, foiling their plans, and Urianger convinced them that killing the WoL would speed up the process in causing a calamity.

Their initial casual approach, alongside our new understanding of time between the stars, suggests to me that at that moment, time was moving very slowly on the First in comparison to the Source. While the flow of time was in this state, the WoDs had plenty of time to cause a calamity before the flood could overtake the First completely. In fact this could very well have been going on ever since Lahabrea attempted to cause a calamity with Ultima weapon.

If you consider this possibility, then Minfilia's involvement would have been unexpected, but not entirely unwelcome, as until she halted the flood they would have been working on a strict time limit. Minfilia's actions therefore would have foiled Elidibus' plot, *but* also given him all the time he needs to create a calamity to usher the rejoining.

That is, of course, until we arrive on the First, kill Emet-Selch, and remove a great deal of corrupted Light from the shard. Now, I personally don't think the shard is out of the woods yet. The Eden raid will very likely, imo, go deeper into the Sin Eater lore and reveal the source of the Sin Eaters, which means the First wouldn't be truly safe until the Eden raid is dealt with. But things have gotten so messed up that Elidibus clearly has no idea what will happen next. He's winging it now.