Shortly after, Poseidon became the God of the sea, earthquakes, and horses and so every night when the sun would set Poseidon and Nyx would have to meet and discuss the transitions from day to night to create the most beautiful sunsets. Since no one was in charge of the day sky, Poseidon was the only one that could work with Nyx. As the days passed, Nyx noticed herself eager to see Poseidon and create beautiful scenes with him. One evening, Nyx decided to invite Poseidon to one of the celestial gatherings. This was going to be a special one since they were going to introduce the biggest full moon of the year.

Poseidon agreed to go since he cared deeply about Nyx and felt they had formed a bond with each other. He had not met Selene yet since she had been gone for a month creating a galaxy light years away. Knowing that she was an important person to Nyx, he wanted to set a good first impression. He decided to show up with a gift for both Nyx and Selene: a chariot with four white horses with long silver hair. As he walked into the party offering his gift to Nyx and Selene, when his eyes met Selene's and her eyes met him, it was love at first sight. The horses reminded her of her beautiful moon, and his smile made the hair shine brighter than usual. Upon seeing her long silver hair shining as the full moon brilliantly glowed behind her, Poseidon couldn’t help but feel an instant connection with her.

Nyx instantly realized that they had fallen in love. Selene was more than a best friend to her, she was her sister. So, she decided to keep her love for Poseidon hidden.