Ooh I have questions about the Twisted Spire now! You mentioned it knowing usurpers and pretenders, does it know when someone's been disinherited? How long would it take to react to that kind of ruling? (Can it decide for itself if someone isn't worthy of the throne/their magic?)
I'm loving digging into this thread of lore thoughts!! So, warning: this'll definitely get long π¬π Thank you so much for asking! π₯°
By Kiramean tradition, a sovereign waits to declare the crown heir until all their eligible heirs have reached the age of majority (patience is a perk of living 2 centuries). The eldest is the heir presumptive only in the sense that they inherit if the ruling monarch dies before naming a crown heir. This works out to the immediate family of the current monarch all retaining their magic within the palace enchantments for most of their lives, as well as a monarch's parents and siblings who live in the palace. Those who move out of the royal apartments and no longer call the palace home, however, seem to waive their membership; royals outside the line of succession merely visiting no longer have the privilege of their magic.
In the less common instances where an heir is named outside a king or queen's nuclear family, the heir gains access to their magic in the palace upon being named. In one notable case, a king named his niece his heir on his deathbed, and his scribe brought this news to the court, gathered for the king's imminent passing. It was received controversially, at first believed to be a concocted scheme--until she proved her inheritance by conjuring and flinging roughly a pint of mud into the face of the man accusing her. Can't argue with the palace itself, right?
On your other question--no, there isn't an instant of delay in the palace recognizing the succession. There have been multiple moments throughout history, I would imagine, in which the children of heirs are the first to learn their grandparent on the throne passed away, because they suddenly felt they could draw upon their magic in the palace, and siblings of the monarch learning by way of losing their magic in the palace that their sibling's child (and immediately heir-apparent, redefining the immediate royal family) has just been born.
Because of all this, the Kiramean royal family has a very strong hold on the throne, because the palace enchantments are seen, depending on your theological persuasion, either the endorsement of the Essence itself (the deified force of magic) or of the founders of the Kiramean Empire, the Volandi.
In The Volandi Saga, my novel series in progress, these historical scales will be put to the test in a new way. We'll see that in fact it is possible for the reigning monarch and the palace enchantments (laid by the founding sovereigns of Kirame) to be at odds concerning the issue of succession. This will come to bear in a big way later in the series, so I won't say much more just yet, but the judgment of the palace quietly observing in the background is a force at play in Kirame that quite definitely should not be ignored.
Now, you might be thinking, surely this pool of eligible heirs, combined with access to magic in the seat of the sovereign's power, must create a fertile environment for assassination plots? And you might be right, if not for another vestige of ancient Kirame: the AshantΓk, a challenge for the right to rule by combat to the death between an heir and a ruler. Both are allowed a sword and their magic, and the vanishingly rare few times it has been invoked, the palace enchantments have instantly honored the outcome.