Alhazi Invasion (often just "Alhazi" or AI) was a Diku-derived hack and slash MUD. Loosely based on medieval fantasy, it offered an extended character class system with sub classes, 80 mortal levels, player killing, and a clan system with clan halls and clan-owned areas, among other features. The game world contained over 10000 rooms in over 100 areas of varying quality. The player base was mostly Singaporean and North American. The highest player peak ever experienced was probably about 40–45 characters online simultaneously, but usually there were considerably less people around. It has recently been restarted, see external links.