Those Who Went Missing (TWWM) is a collaborative world-building game centered on the Esk species and their world. Its online community gives members tools and activities for developing characters, exploring shared lore, and participating in ongoing stories and events. The site features a world guidebook, species masterlist, user directory, and resources such as a point calculator, alongside news, staff notes, and community discussions.

Members can take part in monthly writing prompts, seasonal events, quests, and adoptable sales. The site also runs a Greenhouse program, where Esk characters are offered through themed releases with different types and point costs. Adoptable opportunities include guest artist and staff sales, such as batch sales and auctions, with guidance available for artists interested in contributing. News posts provide event updates and clarifications, while sightings introduce story details and non-player characters from the setting. Through these features, TWWM combines collaborative fiction, character creation, community participation, and a structured system for acquiring and developing Esk.