Slash. Harry is in love with locket Tom but has promised to return the horcrux to Voldemort

[Guest TomarryForever]

Harry is attending another magical school that's not Hogwarts. I believe it's Durmstrang, but am not sure... At some point he acquires the locket horcrux and befriends the soul piece within, who is his confidant and friend as he goes thru each year of schooling. He keeps it safe and secret. My memory is really fuzzy about what else happens in this fanfic, Harry's name might be changed and I'm pretty sure he didn't live at the Dursley's during his entire childhood. There may have been a HP/OMC brief relationship.

I recall eventually Harry meets Voldemort and promises to give him the locket, but he at that point he's truly in love with the Tom in the locket, so it's with great reluctance and bittersweet feels that he hands the locket over to Voldemort who plans to merge with it. Locket Tom had to pretty much demand Harry to uphold his promise. Voldemort and Harry agreed to an alliance or maybe a relationship, can't remember, but Voldemort mocked Harry about his attachment to the soul piece, out of jealousy perhaps?

M/m slash. Dark of Grey Harry. Different school. Long, older fic. May be WIP.

[Guest Fallenangel]

This might be the fic your looking for its been a minute since ive read it but it fits your requirements harry goes to durmstrang sirius is his father/godfather etc 

Its called The Black Heir 

https://m.fanfiction.net/s/3762636/1/