Add a new Rule to the Ruleset.  Give it the title “The League” and give it the following text:

Each Breeder has a Rank stat, tracked in the GNDT under the column “Rank”.  A Breeder’s Rank is always an integer and never negative. New Breeders have a Rank of 0.

If both Breeders involved in a Duel have the same Rank, the winner of the Duel gains 1 Rank when the Duel ends.  If the loser of the Duel had a Rank of at least 1, then the loser of the Duel loses 1 Rank.  If more than one Breeder somehow wins or loses the same Duel, or the Duel is cancelled because the Invitee does not join the battle, no Rank shall be gained or lost.

Set all Breeders’ Ranks to 0.