I like Poseidon cause he is sexy.
Forgot that sexy. For that too, Poseidon is the best.
Actually, he was supposed to be sealed for several thousand years. He only briefly got awakened during the previous Holy War (and wasn't suppose to wake up during the modern era, but Kanon forced him awake).
That's true, I think that's exactly what Athena supposed, but Poseidon also boasted that Athena's seals got nothing on him. And I kinda believe this. Now I don't remember every tiny detail, but I remember wondering why or better how he manifested himself again in Julian during Hades arc if Athena had seemingly sealed him again in that amphora. (I usually jokingly say that Poseidon just faked it and currently lives in Julian's hair, thats why it's so damn - it's full of [strike]secrets[/strike] sea god!)
Had the Poseidon arc happened or not (aka. had Kanon forced him to wake or not), and no matter how long Poseidon was supposed to slumber in the beginning, I think he would have had something to say and act with Hades anyway because... well, oceans of earth are part of his realm. Having that eternal darkness and coldness and shit around would have possibly done some damage to his kingdom too. Things seldom go as planned and I dont think any god would just sleep in there when the realm he or she governs get messed by other, god or mortal.
And now I quit this 'what if'fing. Sorry everyone... :')