I haven't watched the marineford but I'm pretty spoiled already so I don't really mind being completely spoiled at this point, But there still some points I might not know so make sure to tell me.

Eden Nathaniel Zero my OC, Would first be confused about what world he has landed (Eden has had multiversal adventures prior to this so he immediately knows he's in a different universe just from his artstyles difference) Seeing and learning that there is going to be a war Eden would immediately try to seek knowledge about war and what is going on in the world he would probably encounter and find someone like coby to ask for help. (since Eden has gone on many multiversal adventures he can recognise which universe is directly connected to his own and which is a unique world Knows this universe is different from his own so he can mess around here without causing a rift in reality)