In RISK, you earn Ranking Points from 'Play friends' and 'Global Domination' multiplayer matches only. The RISK ranking system is a modified version of the ELO system used in Chess. The reasons for this approach are: 

(1) It rewards the quality and consistency of results over sheer frequency of playing. 

Ranking systems that are purely based on wins, defeats and losses only are easily exploited. In our ranking system though, three good results, for example, will gain more ranking points than ten mediocre results.  

(2) It takes into account the relative skill level of players.

The number of Ranking Points gained or lost from a game of RISK takes into account the strength of your opposition. This means beating strong opponents gains more ranking points, and losing to weak opponents loses more ranking points.

Q: I won a game against 5 players, but my rank went down?

This scenario is possible for 3 reasons: 

(1) A player of similar rank scored more Ranking Points in a separate game. Let's say you defeated 5 mediocre players of a much lower rank in your game. At the same time, in a separate game, another player (1 rank below you) beats 5 players of a much higher rank. In this case, he/she would receive more Ranking Points from their win, which could be enough to move him/her above you in the ranks (and push you down).

(2) There is a delay of up to 24 hrs in the server calculating Ranking Points. Let's say you lost one or more RISK games before your current win. It's possible the negative ranking points (and your rank position) from these losses were processed by the RISK server at the time you won your current game, causing your rank to go down.

(3) RISK games can take several hours to finishIt's possible that you lost a game [A], quickly joined a new game [B]. Game A last longer and so both games finish around the same time (and the results are calculated around the same time). You may have lost more ranking points from Game A than the points gained from winning Game B.