Actually , my first thought was that place looks an awful lot like Naboo at night....
I am thinking the Sith have their own version of Force Ghosts. Maybe they can possess people (clone wars) or maybe do an undead thing (Snoke) or maybe both.
I say the Emperor has done just that an was looking to get a powerful apprentice in Kylo. I also think Palps would have wanted Luke out of the picture and maybe even possessed him for a time, giving some disgruntled fans a reason why “perfect” Luke almost Killed Kylo.
Now Kylo realized he has been played by Palps into killing his father, (which Luke couldn’t do) and wants payback (So Rey and He join against a greater evil)
Luke returns to save both of them, since Rey is a Skywalker, and Kylo is also.
Luke ends up fighting Palps one on one, but in the end they all cannot defeat him.....
Que Heavy breathing of Vader........whos suit melts away to reveal pre fall Anakin, (Hayden) who defeats Palpatine once again, with his entire family finally ending the sith.
Rise of Skywalker. (From the Dead)
Sent from the inside of a giant slug in outer space.....