Tournements, Clans and Sieges

am i right in thinking that you need to be a member to join any of the above.
Also what is a siege?

There has been very occasional exceptions with the former, but don't expect to get into one if it ever happens again. To play in them you do need to pay up.

With sieges a player defends (as black) a board against challengers in the order they signed up. As soon as they fail to win, the challenger take hold of the board and has to defend.

thanks