The last ability of Queen Marchesa (long may she reign) checks to see if an opponent is the monarch as your upkeep begins. If no opponent is the monarch, Queen Marchesa's (long may she reign) ability won't trigger at all. Queen Marchesa's (long may she reign) ability will also check to see if an opponent is the monarch as it tries to resolve. If no opponent is the monarch at that time, Queen Marchesa's (long may she reign) ability will have no effect.