Games involving social collaboration

Hi, I am trying to build a social game with the following (loosely-defined right now) mechanics: You join another person or a group of people on a quest for around a week. For every day you are on the quest, you have to perform an action in the real world (like exercising). The more people that perform that action, the more XP/rewards everyone is able to earn What are other such games/gamified apps that you can think of? Essentially I am trying to harness social influence in order to help people build better habits/behaviors. My solution currently broadly involves having 1 or more anonymous people work together to complete a task like perhaps killing a monster together or growing a tree together. Are there other games with similar mechanics that I can use for inspiration? I know of Habitica but that's about it.