AfricanProdigy14
Make him marry a god from another pantheon amatarasu from shinto or even freya from norse or isis from egyptians. Tiamat which is a primordial from babylonanian religion. The morrigan From ireish origins. Or even a primordial maybe gaia? Or nyx or ananke. hecate the titan is also a good match. He is strong independent god and needs a strong god or woman to equal and match him. Also mayeb make a domain stealing weapon, if zeus ever commits crime poseiden can steal his domain and divinity. that way posieden is a the judge and peacekeeper in the greek mythology. make him learn all sorts of combat and warfare from all pantheons and maybe become heir of a fading primordial like eros or erebus. make him learn magic from all pantheons and especially norse runes. but also bathe in dragon blood to gain magic resistance. good against curses and stuff like that. find a way to make sure fates are loyal or favourable to you. So far its good. good luck
Please don't make him OP! All the fanfiction that have OP main characters are garbage that have no future. All of them are unfinished and are rushed because there is no development to the character, also remember that when it comes to open relationships like harem, in real life the woman will also have a few other lovers on the side, not only the man. If you want harem than 2 should be your max, also if you plan on making him op than do it slowly, show us how he evolves not suddenly overpowered where the planet can shatter from him sneezing like other fanfiction that are garbage.