From the introduction:
Games Master Note
Fulsgar and the Mercenary Guild are provided for use in any campaign. It can be used as a source of mercenary employment, militia and warrior skills, spells and training, and perhaps to provide a focus around which a group of Player-Characters can be focused. The cult also contains routes for promotion from warrior to sergeant to officer, and provides background for Runelevel professions for both Player-Characters and for Non-Player Characters.
Though each god is given a name, the names can be readily changed. Fulsgar can even be quickly adapted to become a purely secular mercenary guild, without any Divine overtones, though the Divine spells add significantly to a warband’s capability. The Open Cosmology is provided to locate the cult within a cohesive mythos and to justify its role in the world, but the cult and history is flexible enough to allow it to be slotted into almost any other mythos.