You've given us a superb indulgence of horror here, Dirge! Incorporating the details from F3nix's beginning deftly to twist our perceptions of Flynn as we learn the true extent (and nature) of his dark desires. You swiftly remove the sweet calm of the time in the kitchen with Agnes to speed our pulses as our eyes devour every line.

Lies. He’s aiming for ethos. To hook you in the heart.

I had thought this was a thought formed from Flynn's guilt over the contents of the suitcase (and what he does with it/her) transferring itself as anger over the Father's invasion of his privacy. But, after reading your ending, I've the feeling that it's the voice of 'Tatiana' whispering within Flynn's mind to hold him within her seductive thrall.

Your ending was perfectly paced with Flynn going past the point of no return as his jealousy takes hold to brutally end Thoram's life. Love your final line which leaves me to wonder if the succubus was whimpering over the loss of Father Thoram (another man she'd likely fed upon) or if she was whimpering in delight for how intensely attached Flynn is to her.