From the introduction:
To play Mappa Mundorum online, each player should have a separate blog. Ideally, they should be able to edit posts, allow signed and anonymous comments and screen comments temporarily. Also, they need access to the Map Generator software or a set of pre-generated maps.
Each player controls three Agents and one Planet. Agents are defined only by location and a few changing values, though each Planet (Horus, Astarte, Earth, Baal, and Osiris) is well defined. All planets reside in a single solar system and the planetary orbits are significant. The author developed software to generate and print random solar systems but it was never completed - the rules offer a single map.