Misinformation is one society's most pressing issues, spreading division and chaos across the globe. Videogames have become one of the more promising mediums for misinformation interventions, teaching players common falsehood indicators and helping them develop their discernment abilities. This thesis details the design, playtesting, and evaluation of a digital game intervention intended to improve players' misinformation discernment abilities. Through a design narrative, it first describes the design goals and development of an initial iteration of "DoomScroll," a modified version of the popular social deception game "Among Us." It then reports on the playtesting of DoomScroll and how player feedback was used to refine and improve the mod's gameplay. It concludes by detailing a randomized control trial conducted to more rigorously test DoomScroll's efficacy as a misinformation intervention tool when compared to a control condition. Player feedback regarding its socialization and replayability suggests that DoomScroll did meet its design goals by improving player motivation and increasing the likelihood of repeated use. However, further analyses showed that the mod did not produce any statistically significant improvement in players' discernment abilities. The qualitative findings were more positive, suggesting an uneven distribution of process-driven learning did occur. This study contributes insights to improve misinformation game design and into the potential of modding as a medium for educational game development. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]