If you partook in the Halo 5 beta last December, it's highly likely that you found yourself placed into a division. Some of you were lucky enough to place into a special tier called 'Semi-pro' and 'Pro' for you exceptional gaming abilities. Yesterday, 343 Industries blew the lid off of refined division system that you will see in the retail version of Halo 5 Guardians.
Competitive Skill Ranking (CSR) is 343 Industries' call to action for more competitive ranking in the Halo experience. It operates on a per-playlist basis, so those who earn one of the coveted tiers, need not worry about losing it during a day of Weekend Social matchmaking with friends. This ranking is based on wins alone, and will be used to determine your matchmaking teammates and opposition.
Similar to the beta, your first ten games in Halo 5's Arena mode determine your starting placement. Once you've completed your first ten matches, you will be placed into one of seven tiers (bronze, silver, gold, platinum, diamond, onyx, or champion). From there, you'll progress through a series of ranks within those tiers with hopes that you can eventually make the jump to the next tier and so forth.
The CSR system operates solely on wins, not individual play. As continue to win, you will continue to climb the six ranks in your division. A string of wins at the top rank will earn you a spot in the next division up. 343i was also keen to note that once you reach a specific division, you will never go down in placement. This means that once you are in the Gold division you cannot be demoted to Silver.
The last two tiers, Onyx and Champion, operate a bit differently from the five that come before it. A player who reaches Onyx division does not have tiers, but have a number that displays their current CSR score. Winning matches will then increase your associated Onyx score so you can more precisely gauge the scores of players. Out of those Onyx players, the top 200 players with the highest CSR score will be promoted into Champion league.
You can view each of the ranked tiers below: