They have a rules page, if anyone missed it.
"To take part in the event, you must have at least 1 of the 7 following characters in your Deck (the seven exes): Wesley
When characters are selected from your Deck for a fight, if one of the seven exes appears in your Deck, it will always be chosen first.If you have more than one of the seven exes in your Deck, one of then will be randomly selected first.
For fights to count, they must be launched by 'QuickBattle' in one of the following rooms: (all formats)
The event will stop when the total sum of wins achieved by players hits 777 777
There will be a ranking table for each of the seven exes showing which players have achieved the most wins.
There will also be a ranking table for players having obtained the most wins during the event with all the different characters put together."