Also, it’s just come to me what Alastor’s plan is.
Alastor demanded that Rosie make him stronger because he couldn’t defeat Adam, which Rosie pointed out being the strongest sinner doesn’t make you as strong as an Archangel.
Alastor then sings “Don’t you forget” with Rosie and then cracks outside only to realise what’s his next move, "fighting" the Vees and then surrendering, tipping the balance of Hell.
This all came to me thinking about the Speaker of God vs Vox, and how if even Alastor couldn’t compare to Adam, how would Vox compare to the Speaker of God. Then it hit me.
Vox united the Overlords likely to steal their power and then Lucifer’s. Following this, Alastor’s deal would not be met and either Rosie would need to give him more power possibly more than she can give (or maybe not if she’s Roo/Rue).
Meaning either Alastor gains unimaginable power, enough to conquer the cosmos after Vox is defeated or he’s free of him deal with Rosie and can do what he wants.
Either way, he wins.