Threshold is a roleplaying enforced MUD (Multi-User Dungeon) written in LPC with a custom code-base that has been in operation since June 1996.Its focus is on providing a place for roleplaying, as opposed to working as a traditional game. It has as many as 70 players online at any given time and is ranked in third place on the all time ranking list of Top Mud Sites. In 2001, the game was mentioned by Computer Gaming World in an article about online games. Threshold was also the primary MUD example quoted and discussed in Edge magazine`s article, "Lost in Transition" which discussed the preservation of gaming history.

Threshold RPG is a fantasy based MUD set in a world with three main continents and a chain of islands. Religion based on a pantheon of Greek-like deities plays a dominant role in the story of the mud, with the ability for players to rise through the ranks of religious organizations to gain divine powers. The concepts of good and evil serve as a core driving force of the roleplay within the game. Threshold provides a framework for a player-driven legal system where players can take the role of judges, lawyers, and the jury in order to prosecute players who are accused of breaking the law. There are fourteen guilds in Threshold which are equivalent to character classes in Dungeons & Dragons, one being a secret, unlisted guild. Players can diversify their characters further with skills acquired by joining a clan.

Threshold started out with a donation system where players donated towards server upgrades and hosting costs. Then Threshold evolved to a registration system with a yearly subscription fee. In 2007, Threshold became free to play with a pay for perks system where players can purchase virtual items.

For three consecutive years, Threshold was The MUD Journal`s highest-rated role-playing game. Computer Games Magazine listed it as a highlight of less popular MMOGs, describing it as being particularly focused on role-playing, and noting the distinct passion of its players. Richard Bartle described it as possessing an "individuality" lacking in other, contemporary graphical MMOGs, citing its in-game legal system as an example.

Taverns and cafes make up a prime component of Threshold, where players meet to chat, enjoy a drink and buy some food.