Alucard put Dracula in the coma with the sword, basically something we've already known.
Victor is killed by one of Satan's servants (it's not described how he was killed but hopefully not like a bitch.
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Carmilla is *gasp* not real and is apart of the castle manipulating Dracula's mind.
Alucard is getting his own DLC chapter (shocker I know) and will act as a prequel to the events of LOS2. It takes place in the city before Dracula's awakening and it's about Alucard's plan's for Dracula and Zobek. It's slated for a March release and unlike the first game's DLC, this was in development simultaneously with the main game.
Final boss is Satan (surprise!) and he summons his Lovecraftian looking pet Leviathan, who can instakill the planet in one hit. You fight Satan at the top of said leviathan.
During the fight with Satan he takes control of Alucard and you're forced to fight him. (Called that a year ago BTW
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You fight Dracula's doppleganger.
The game ends with Dracula beating Satan, Dracula and Alucard leave to the cathedral that Dracula wakes up in before the sun comes up. They reconcile their differences and become family again.