I just got an ask for a love letter Yandere Philip would write for his Beloved... (I will write an actual love letter from him, just have to decide if it's to a human!Reader or a witch!Reader).
That got me thinking about if he did pine for someone in the human realm. Just think about all the love letters he'd write while in the Boiling Isles that were never sent. The stack would rival Eda's school record.
He'd be in denial that this person would never move on without him (though they may have never known he was into them), and he writes them as if he and his Beloved are set to be engaged. He'd lament to them about having to stay in this 'awful place' in order to save them from evil and he'd be 'home' as soon as his mission is complete. When he realizes that too much time has passed and his Beloved is no longer alive, he goes into full-on denial.
Throughout his years in the Boiling Isles, he has caught glimpses of people that look like his Beloved and those people would disappear from the public eye. He'd keep them (against their will) for a while, shower them with affection, and make them look even more like his Beloved, but when he either got bored or reality slapped him in the face, he'd dispose of them. They were still witches, after all. His Beloved is not a witch, no matter how much they look like them and cutting off the tips of their ears only did so much.
Once he perfected sigil magic, this process became easier, immobilizing his target and allowing him to whisk them away to his hideout and repeat the process over again. He'd also lure them away with the line "The Titan has specifically chosen you...".
When he became emperor, he had a chamber built off of his bedroom that would house his target until their demise. It's soundproof and windowless and absolutely no one in the castle knows about it. If Belos gets wind of someone having knowledge of this chamber, they are swiftly dealt with. He may either invite his target, have his coven scouts bring them to him, or go get them himself. An illusion of the victim is always seen leaving the castle so no one is any the wiser that they're still locked up inside.
