The Glorantha Sourcebook - Rules of Play says:
The Glorantha Sourcebook is an essential resource for Greg Stafford’s world of Glorantha, one of the most extensively developed and renowned fantasy settings of all time. A world of mythology, gods, and heroes, Glorantha has inspired roleplaying games, board games, computer games, comics, fiction, and more, a setting beloved and revered worldwide. An invaluable resource for gamemasters, players, and readers of fantasy worlds, this sourcebook is gorgeously illustrated and filled with informative maps and diagrams. Drawn from a variety of out-of-print and rare sources, this material has been dramatically revised, updated, and expanded. Alongside this foundational material are new essays, insights, and extrapolations on the world and its incredible denizens.