Bab 1386: The Sea and the Heavens Clash

He sighed. 

  'Brother. You might not think of much of my palace but I am worried' then he added

'That you could so easily enter my Palace' 

Today, Hades had shown some of his capability. Maybe, it is simply because he was unaware of what his action implies.

Or maybe, Hades knows exactly what he was doing and he is sending a warning or a reminder. That there are still many things that the Olympians don't know about him

Domain of an Olympian is not easily breached. 

But Hades simply come and go whenever and wherever he pleases. 

That is not a pleasant feeling for anybody. The worse thing is that Hades place is not like any other Olympians

As far as Poseidon knows, even Zeus had to ask for permission to enter the Underworld. The Underworld is like a separate kingdom that even Zeus has no control over.