King of Dragon Pass is a 1999 computer game published by A Sharp. Set in the fictional world of Glorantha, it depicts the lives and fortunes of one of several barbarian clans, settling the untamed lands of Dragon Pass over the course of several decades.
The publisher still supports the game and has ported it to OS X, Windows, iOS, and Android. For those who want to play it under classic Mac OS, they sell burned CD-only copies at their website for $19.95. For a boxed copy with docs, you'll have to look on the used market.
The version 1.7 update can be downloaded from the official site.