That wasn't what I was talking about, but since you bring it up, civil wars are actually fairly manageable in monarchies. It's not like another form of government where any strong leader can make a bid. Someone needs to have a claim to get support. People had trouble conceiving of anything else. This gets into brutal medieval stuff, because the politics of the era strongly favored bloodshed and ruthlessness, but the basic method is to ensure that the candidate you support is the only candidate with a claim who is still alive, or they themselves are supported by the alternatives. In Europe this was fairly tricky because everybody had lots of cousins and so on all over the place, but this is a very closed system.
The next best alternative is to ensure that your preferred candidate has staked their claim over the military and government apparatus before anyone else knows a succession has occurred, and that makes it very difficult for anybody to do anything about the fait accompli.
As for controlling the public, 'Oh no, wilder assassins have killed the queen, I shall now reluctantly take the crown' would be the obvious approach.
Monarchies may focus a lot on succession of the royal family, but that doesn't mean that a sufficiently critical mass of nobles couldn't bring enough force to bear to cause a war, especially if the new monarch gets caught lying about or concealing major truths such as "the former queen tortured and dissected Wilders and that's why they're marching on our cities". Or hell, even
revealing those truths could cause rioting or a civil war if it's not done very carefully. We know from that soldier Blake saved that there are people dissatisfied with the way the queen's running things and that feel confident enough to say so in an unsecured location, but the fact that the Bitch is still on the throne implies there are plenty of other people who are satisfied and/or actively benefit from the status quo. This implies a divided populace, not one that unilaterally supports the current monarch no matter what happens. There's nothing special about monarchies; they rise and fall based on the willingness of the people to uphold them just like any other form of government, so as long as enough nobles and other people of influence consider Veve to be a threat or just want to make a power grab and change dynasties, they can very easily rouse the commonfolk to arms with the right lies and propaganda. I will admit that Veve seems to have the loyalty of most of the army and therefore could probably suppress an uprising pretty easily under normal circumstances, but these aren't normal circumstances. An army of Wilders managed to invade parts of the Cielan kingdom that they haven't been able to get to in literal centuries, which coincides with five powerful strangers, including a Wilder, showing up and ingratiating themselves with the princesses suspiciously quickly: everybody's feeling unsafe and on edge already and to someone(s) sufficiently clever and power-hungry, it's not too difficult to channel all that fear and turn it into anger that can be directed at the "traitorous princesses" or at the five convenient scapegoats who the princesses will feel obliged to defend.
Furthermore, I sincerely doubt the Queen did this on her own. She built secret laboratory basements in her watchtowers that the average guard wasn't aware of; that alone implies that there's subtlety and organization to this, which means other nobles, mages, scientists, and other people of influence who were actively involved in making this happen and agree with her methods. If it's just politics, then they'll probably be too busy backstabbing each other to be backstabbing us, but if it's more ideological or cultlike, then they're not gonna give up just because we killed their leader. And that's not even counting all the well-placed people who have probably been compromised in the same way Veve was, which could very well include deadman switches in the event of her daughters rising against her. The Queen strikes me as exactly the kind of paranoid and petty bitch to have contingency plans for just this type of scenario, and seeing as we've just discovered this problem and don't know the local politics, we have
no idea who else is compromised, except that it probably includes people who were the most outspoken against her, and probably won't find out for sure until it's too late and they're already carrying out their programming.
Long story short, Ciel is a powderkeg right now and we're about to throw some dynamite on it. If the population
doesn't snap as a result of our actions here, I will be pleasantly surprised, but I see plenty of ways things could explode into city-wide violence just based on the fact that the Queen has mind-altering capabilities and demonstrably isn't afraid to use them, let alone the unknown political ramifications of violently removing her from power.
Finally, this is a narrative-based quest, so I expect x50413 to complicate things one way or another. If we suffer a clear-cut loss, there is a story to be told of how we overcome our deficiencies to win next time; or if we win but with complications, there is a story to be told about how we cope with the consequences of our actions; but if we get a clear-cut win that
simplifies the situation, that suggests a story that is winding to a close rather than being continued, which doesn't fit the structure of a narrative quest. In other words, I strongly doubt that the Queen is this era's final boss, if only because there are so many things we have yet to learn about what's going on.
1. The quest intro, we've been here a long time and are likely the source of the humanoid template.
1. Literally altered the evolution of life on the planet via our presence.
You've been presenting this as a "surety", not a "likely". Besides which, we know there are gods in this setting that could have created humanity without any intervention from us. You have no evidence that we're responsible for humanity's evolution on Remnant and you
especially have no proof that we're the origin of all magic because
the quest actively says you're wrong about that.
2. We have the ability to drop as much or more obsidian energy here as we did then.
2. Blake wasn't yet a living frozen flame at the time. Our ability to deploy our energy is greater than ever.
But our caution is far greater now than it was then. We knew Blakesidian was a risk when we did it, and now we know exactly why; furthermore, we know that massive spacetime disruptions make such a merge even riskier and will definitely not perform the merge unless we're positive there will be no such spacetime disruption or if we
absolutely have no choice. Blake being a living Flame is literally not a risk factor here unless we merge with her again, and even then that's
far more likely to cause long-term problems with Blake's sense of identity than it is to toss us through time again.
4. In and of itself simply being a timetravller is probably not a problem, disadvantage on saves vs. banishment is probably the worst of it under normal conditions. We aren't normal conditions. We have enough things working against us that it's relevant.
4. It's relevant because of the sheer number of factors in play making interference from even minutes r factors more important.
That's
not how this works. That spacetime bomb combined with our only-slightly-restrained presence was what tossed us through time last time, and those are so far beyond the other factors you've mentioned that the other factors
don't matter at all. The greater number of variables this time does not outweigh the sheer weight of the variables last time; or to use a metaphor, just because you have over 9000 skilled archers doesn't mean they can have any relevant effect on two people shooting each other with tanks. There is
no reason to worry about being tossed through time unless
we pull out the metaphorical tank
and the Queen's rocking at
least a metaphorical bazooka's worth of spacetime disruption.
5. Ruby and co did most of the work on the sword, and it's still a factor.
We spent a lot of time plucking at spacetime to make Shroud and Veil open the gate the first time, and that was in an area where spacetime had already been severely weakened and after Ruby had performed a highly context-specific ritual to give us the connection we needed to even do
that. You
drastically underestimate just how much
work it takes to break time that badly.
