In order:<br/><ul class="bbc_list" style="list-style-type: decimal;"><li>It isn't <em>officially</em> invite only but because of the way that travel in the Empire works, someone coming to the castle would either need to have received travel papers allowing them to move in Scorpion lands or otherwise be permitted to use the highway however they want. Functionally yes but officially no, and it would probably be impolitic to imply that it was invite only. If you're in the castle you can compete but might risk rousing the ire of the Scorpion organizers if you weren't on the list to begin with.</li><li>There are not multiple grades of competition. Everyone's competing for the same prize.</li><li>There isn't really a ranking system, acknowledged or otherwise. Reputation plays a pretty big role in understanding who is likely to triumph over who and why.</li></ul>