Challengers is a one game knockout you play against each player in challengers within 15 days. .. Loser reports the game and gets -10 challenger points, winner gets +10 challengers points.

Challengers is not like divisions, everyone (regardles of his/her division) can join challengers

If you don't play a challengers game ( at least one challengers game per 15 days ) then you will be removed from challengers section (you can re-join challengers at any time as long as your game account "Divisions" is active.

Rules for games to be played in challengers are specified by League Admins (After you login, you need to check Challengers rules for the game you joined)

At the end of reset the winner (who has the highest challengers rating) will get an icon indicating his/her challengers victory with some extra ( poggers coins ) as a reward

Extra rules related to challengers are located under (Challengers Rules) after you login and join a game.