The Garden

palpatine never intended to die, in my mind, he just aimed to prolong his life through sith bullshit ad infinitum, so i don't think he ever officially established a successor or even a method of transitioning power. i think everyone collectively assumes vader is his heir, on account of vader being the only person with the horrendous job of actually having to talk to the emperor directly all the time. but there's not anything binding except for the fact that if darth vader wants the imperial throne, he can crush the litany of people who would like to stop him like bugs, and i think everyone would assume in turn that vader - a guy who is famous for his frothing at the mouth about the empire's Divine Vision For The Galaxy - would want the throne.

this is, categorically, false, because every single time he's thought about killing palpatine, he had someone else he wanted to hand the throne. this is an awkward situation in which everyone is waiting for vader to stake his claim on the throne in the immediate aftermath of palpatine's death, and vader's like [automated breath] i..... have...... rebels.... to kill......... but i think, as horrific at diplomacy as vader is, he's at least savvy enough to know that the second he corrects everyone and tries to cede the throne, the infighting as everyone makes a play for the throne would cause a ridiculous amount of unrest. so he can't just cede the throne, but he's next to incapable of being functional without serving His Imperial Majesty's Divine Vision, and he needs to choose a successor as fast as possible and then he can possibly consider finding a ditch to lay down in because his one last attachment to the mortal plane died.

i know it'd be more reasonable for vader to kick punt someone like tarkin at the throne, but consider that vader is, fundamentally, unreasonable. and at this point in time, he's also famous for being kind of a religious zealot, and he would absolutely choose this particular time of all the times to trust in the force. so he meditates, considers the sane options, but the force keeps lingering on senator leia organa from alderaan - and it's doing that because she's secretly his daughter, but he doesn't know that, and theoretically this is enough ahead of ANH that he doesn't even have an inclination that she's a rebel spy. but if the force wills it.

so leia, all of eighteen years old, is named empress by darth vader and he doesn't have the grace to tell her he's going to name her empress first, he just kind of goes in front of the imperial senate and does it. i think it would be utterly hilarious if vader handed the empire over to the rebels without knowing it, handed the empire over to his daughter without knowing it, and now leia has to figure out how to safely un-empire an empire while being empress without causing too much chaos.

which is not a job made easier by the wheezing war criminal who keeps kneeling in front of her and asking, "what is thy bidding, my master," because leia has unknowingly inherited the weirdest position in relation to vader anyone could have, and he's kind of relying on tradition to cope. i really just want you to imagine an ongoing bit where one of vader's cybernetic arms gets wrecked while he's suppressing a coup organized against the new empress, and he leaves it like that for weeks because palpatine always had to clear off significant changes like replacement prosthetics, and he keeps waiting for leia to do it. she finally snaps at him to just go and get it fixed, and vader's thrown into an array of distress because that is NOT how this works!!! his MASTER clears off his medical procedures, it ALWAYS works like that, and leia's confusion is bone-deep, because obviously that only makes sense to vader.

wouldn't vader notice the empire getting un-empired by the new secretly-a-rebel empress, you wonder. i would say that he probably wouldn't, because as horrific as palpatine was, he was also all of vader's will to live, up until the moment leia shows him a singular basic courtesy - like not being weirdly involved in the process of vader getting a new arm - and vader decides that he is going to froth at the mouth about Her Imperial Majesty's Divine Vision, instead, until she sees fit to grant him death.