because the guy that dives off Olympus (with tatoos) summons Leviathan, and summoning leviathan is what Poseidan does. I think they mention it on the gametrailers episode.

^ i didn't hear his name said at all. i doubt that it's him. he's much too important to be the first boss.

libellule quickly leaving this massive spoilers thread
I have the gametrailer video but I didnt know the guy you killed first was ... this guy.

also, I never have seen anything related to "300" in the video ...

He was talking about how Spartans would form a dome with their shields and stick the spears out. This was done in the movie 300.

btw, why are we sorta trusting something from gaf? ^.^

http://www.gametrailers.com/episode/gametrailers-tv/85?ep=85  

You probably weren't paying attention >_>.

Start watching exactly at 3 minutes into the video. You'll see a dude dive off the mountain and take out a titan by himself..(I DOUBT a henchman could do that, so you know that guy is strong as hell)

Then after the titan falls into the water, you'll see the water stirring into a whirlpool which leads to leviathan popping out and attacking Gaia.

At this point, you'll be around 3:46 into the video, where Geoff says that the monster turns into Poseidan at the end.

I'm not guaranteeing that it's poseidan that dies via second person, but here's what we know.

• That sequence happens pretty early in the game
• You fight leviathan early in the game
• leviathan is summoned by Poseidan (or turns into Poseidan)
• Kratos is not afraid to fuck the Gods up with his bare hands (look at Helios).

It's very likely that it is indeed poseidan, whether some ppl at gaf says so or not, it's logical from my standpoint.