From the Patch Notes:
Players receiving the top rank in any category are guaranteed fantastic prizes at the end of the month!
Players within the ranks of 1-25 for Colosseum, Brawls Won, Draft and Duel categories will receive 5 Draft packs among other prizes.
Players within the ranks of 26-100 for Colosseum, Brawls Won, Draft and Duel categories will receive 3 Draft packs among other prizes.
Players within the ranks of 101-250 for Colosseum, Brawls Won, Draft and Duel categories will receive 1 Draft packs among other prizes.
A unique shop will be available in the future and will feature exclusive rewards for those who rank highly within various Leaderboard categories.
Level, Cards owned and Unique Cards owned will receive cosmetic rewards only.
Colosseum and Draft categories use a point system for ranking.
1st Place – 5 Points
2nd Place – 3 Points
3rd Place – 2 Points
4th Place – 1 Point
Leaderboard information will not update until Midnight server time.
Feel free to discuss your opinions on this addition to the game.
Personally, I feel that leaderboards will mean absolutely nothing for the vast majority of people. Only the highest elite whom have spent the most amount of money on this game will be able to achieve high positions in any category. For collections, the majority of epic, legendary, and promo cards are closed off to free players, even with the occasional luck from drafting. For anything involving the use of energy (brawls and levels, for instance), paying players who have bought countless energy refills will win there by default. Etc.
Also, considering that being at the top of the leaderboard gives “exclusive rewards” and “other prizes”, people higher up in the leaderboard will gain the tools needed to maintain an advantage over those not in the leaderboard.