In this study we use moral labor to denote a particular form of work primarily driven by moral sense - people believe it is right to do so and such work is utilized to improve commercial product. We examine moral labor in League of Legends, a popular online game. The game's developer, Riot Games, built a crowdsourcing platform that solicited free labor from players to deal with massive toxic behaviors including trolling, griefing, and bullying. Our ethnographic study of the game revealed how players willingly contributed their moral labor to improve the game regardless of rewards. We also found inherent tensions between players' moral sense and Riot's corporate agenda, manifested in the differences and similarities between the narrative of players and that from Riot, which evolved along the release, maintenance, and closure of the system. We consider future research directions on the relation of moral labor to online community.