Crossfire is an open-source MMORPG that has been around since 2001. It is for UNIX but now also has a Windows port.
This game resembles a multiplayer NetHack, but not exactly. You play on a square grid, go into dungeons, kill monsters, and collect unidentified items.
You can download a client from Crossfire's official web site.
Crossfire provides examples of:
- Explosive Breeder: When you walk near a breeder, it starts breeding. If you don't kill them quick, the breeders may fill the entire area. Newbies may accidentally have the "Beginners" dungeon fill with mice.
- Global Currency: All shops take silver, gold and platinum coins. Prices are in "gp".
- Noob Cave: The "Beginners" dungeon is a tutorial. Monsters wait behind gates, so they don't attack players too soon.