If you imagine that MMR has the range of 0-1000, then the following MMR values determine which league a guild is in:
0-100 Copper
101-350 Silver
351-650 Gold
651-900 Platinum
901-1000 Diamond
MMR is adjusted based on battlefield placement according to the number of guilds in the battlefield, as such (again using a MMR range of 0-1000):
Place | 8 Guilds | 7 Guilds | 6 Guilds | 5 Guilds |
---|
1st | +175 | +150 | +125 | +100 |
2nd | +125 | +100 | +75 | +50 |
3rd | +75 | +50 | +25 | 0 |
4th | +25 | 0 | -25 | -50 |
5th | -25 | -50 | -75 | -100 |
6th | -75 | -100 | -125 | - |
7th | -125 | -150 | - | - |
8th | -175 | - | - | - |
In addition, if a guild has been elevated to a higher battlefield (such as a gold league guild participating in a platinum league battlefield), then any losses are cut in half, and any gains are boosted by 50%. So an elevated guild that finishes 2nd in a 5 guild battlefield would receive +75 to MMR instead of +50.
With an MMR range of 0-1000, the prestige awarded at the end of each season is equal to MMR * 18.