Expedition adds a new challenge mode to the game. Generate a list of random or hand-picked challenges and embark as Monk, Survivor or Hunter to complete them. Finishing an expedition will award points which count towards unlocking new perks and abilities for you to use in future runs, or even burdens to increase the difficulty in a variety of ways in exchange for more points.
You can find more detailed information about the mod from it's GitHub page below:
https://github.com/LeeMoriya/Expedition/