3rd annual offline tournament "Best of the best"

Are you playing in the interportal tournament?

I'm still getting used to the royal games on the Portal. Things haven't been easy this year... I know about the interportal tournament, but I haven't looked at the map yet... If I have time, I'll play...

But what exactly is the "interportal" aspect of the tournament? It doesn't seem to be commented on in the rules. On HP, the tournament is held as part of the ranked tournament in the "Other Tournaments" category...