I have no clue about how rankings work. You can move down when you win and you can move below someone you beat. I can tell it's a system of how many pluses there are ahead of you that causes you to drop. I noticed that there were 3 fighters in my group that all wnet ahead of me with more than plus 300 ranking climbs, one at plus 450. Is this because the players are buying a ton of trophies and spending them all at once, or is there a way in just fighting that can boost a guy that high?
Steppe Wolves