Instance shard world

An instanced shard world is a world (or server) sharded off from the rest of the servers. A player cannot access an instanced shard world except through specific means; activating a trigger or teleporting to said location.

RuneScape's first instanced shard world takes place in the form of Clan Citadels; when a player accesses the Clan Citadels portal, they are taken to the shard world specifically designed for their clan. Every clan has their own personal shard world, which allows multiple clans to co-exist on the same map without interfering with each other. This allows clan mates, regardless of their actual world number, to interact with each other at their citadels.

Trivia

 * Shard worlds first became a popular term in the MMO game Ultima Online.
 * Instances were popularized by the MMOs World of Warcraft and Everquest.
 * The term 'shard' refers to a splinter server, compared easily to a piece of wood or rock 'shard' splintering off from the main object.