NCF – Extended list of Neutral creatures.

Not Neptune, but Shalassa, I agree with psatkha. But it doesn't sound as interesting anymore, and the connection to all sorts of tridents is unclear. You could try to diversify the game's lore and introduce some new, less common cult. Honestly, I was already getting tired of the focus on elemental dragons ten years ago, and Ubisoft made a mistake by making it so one-dimensional at the time. But still, it would be better if it wasn't Neptune, but someone or something else, not such an obvious copy of real pagan religions.