Sorry I can't help but to defend my admired king's actions here. This could unintentionally spoil the story for some people, but if you want to understand the story during the timeskip, I think you should probably read Master Guide books, listening to the lore synopsis videos, or continue through my yapping wall of text here.
Like, I get it, better to put your kid in a coma for 50 years than for there to not be a world in 50 years.
But also, fuck off Endy, what the fuck bro
What exactly was the problem here? Up until the very moment the plan was revealed to Regulus, he still treated him dearly, even asked him for what his son would do in his position. Even then, Endymion didn't say anything about him agreeing with the plan nor threatening Regulus; his indecisiveness is apparent. I guess the only thing you can be angry about him is firing a bombastic energy blast toward him and Verre, but obviously that wasn't him trying to hurt them by any means. So he was just trying to be intimidating toward Regulus. Not to mention Verre's nonchalant actions during that scene there.
Yall talking bout Endymion as if we didnt already know he becomes a giant asshole
The bigger problem is why the hell is normal summon man dead?
When exactly did Endymion "becomes a giant asshole"? He was a great guy when he was young, he stood against his tyranny brother who terrorized the country, and becomes a king beloved enough to have commons and servants who admired him, also Selene specifically. He was also not impressed by Regulus when he tried to take down the sacred eagle, because he's aware of his people. And now he's trying to stop a great calamity by uniting the power from each country. The first thing he did is always negotiation. It takes at least 5 years of that for him to use military forces.
About Aleister, the reason he ended up as a living magical battery is written in the Master Guide 6 as "during an experiment, ended up partially merging with one of those gods or spirits" making losing himself more and more. Not entirely clear, so I'm hoping the following chapter will explain this, since the calamity about to happen is probably about Invoked Augoeides, since La Maison is still operating as normal.