The World
The Living World
The world runs on its own clock. Things happen in it whether or not anyone is logged in to see them.
Day, night and weather
Time passes and the sun goes down. Weather rolls over the land and is reported to you based on where you are actually standing, so a storm you can hear from a cave mouth is not the same as one you are standing in.
Darkness is not decoration
An unlit room is genuinely dark, and being unable to see costs you real information about what is in it. Some races see in the dark; everyone else carries a light source. This is the same underground either way - it is the character that differs.
Hunger and thirst
Both run on a clock, both tell you where you stand, and both eventually cost you if you ignore them. This is what makes cooking a trade worth having rather than flavour text, and what makes a waterskin part of your kit.
NPCs with somewhere to be
Mobs are not scenery bolted to a room. They can follow waypoints, run scripted behaviour, react when you walk in, emote, cast in combat and hold a conversation the world has written for them. A caravan merchant walking a trade road is the same machinery as a wandering guard.
Quests, and Lua behind them
Quests run from kill objectives up to whatever a script can express. The scripting layer is Lua, and it reaches skills, spells, rooms, NPCs and quest logic alike - which is why a quest can be a genuine sequence of events rather than a counter.
Areas, and a map that draws itself
The world is built as areas of connected rooms across three dimensions - the compass plus up and down. Clients that support it draw the floor you are on as you walk it, so you get an automatic map without anyone having to hand-draw one.
Worlds are built by hand
Every room, item, mob, quest and shop in Starfire was authored in a builder's tool rather than generated. That is slower, and it is the reason places feel specific.