At some point, almost every gamemaster wants to create their own Mythic World. That's what the Basic Roleplaying System (BRP) is all about! It is simple, fast, and elegant, using a skill-based percentile system. Combat is fast and deadly, and with a strong focus on non-combat skills that some game systems are challenged to support. Players roll percentile dice against the Gamemaster-led opponents, or even themselves.
At the core, most Chaosium RolePlaying games use a variation of the Basic RolePlaying System, which started with RuneQuest. Call of Cthulhu, StormBringer, SuperWorld, and others followed. Once the Basic RolePlaying System was released as a stand-alone product, more worlds like Mythic Iceland and Magic World were introduced.
So, if you want to create your own Mythic World and leverage a proven system that is the backbone of some of the most successful games in RolePlaying history, look no further.