By default, the challenge roll is 3-in-6, which represents rolling 3 or less on a d6 roll.
A player may elect to increase their character's chance of success by bidding boons, which are fictional factors that makes a task easier, and increase the X-in-6 chance (up to 6-in-6, which is an auto success). Fictional factors that make a task harder are called banes, which decrease the X-in-6 chance (down to 0-in-6, which is an automatic failure). Boons and banes cancel out 1-for-1, which means a given roll should only be made with one or the other.