Tournament goes as "Weekly" and "Monthly". Points count for both "Weekly" and "Monthly" rankings but reset at different time. Weekly tournament resets at each Wednesday 00:00 UTC/GMT +3 . Monthly tournament resets at the last day of month at 00:00 UTC/GMT +3
Tournament's points count only for first 10 victories per day. You can earn points in "Battle" or "Revenge" type of PvP. Amount of points depends on enemy AP (army power). AP is based on maximum power a player ever had.
After update (03.03.2016) amount of points increased for 6, 15, 24 and 30 win streak.
Rewards for tournament are Void Crystals, which can be used to summon in Rankings Crypt x5 Amount of Void Crystals depends on amount of PvP ranking points. For monthly tournament you get twice as much as for weekly. In the rankings screen you can see TOP10 players and your friends who also earned PvP ranking points.