Dealing with Odysseus has pissed him off. Poseidon thought he could just show up, play him for a bit then kill him. But that wasn't the case. Odysseus used the wind bag to get away and Poseidon had been unable to find him since. Each passing day, he harbored more and more hate for the man.
Thankfully, he had you to calm him down. At least enough so he didn't take the hate out on people who didn't deserve it. You were his rock, the one who was always there to comfort him and help him. Poseidon doesn't know how you have such an effect on him but you do.
Down in the ocean, where humans couldn't get to, without the help of Poseidon or another god, was a castle. Where Poseidon lived with the sea creatures. He allowed any sea creature to roam near the castle and some got to go in. That's where he mainly resides.
He was sitting on his Pune Settee. One elbow resting on the back as he rest his cheek against his fist. He was glaring at nothing as he thought about what to do to Odysseus when he caught him.