Magic of the Great Kingdom
After the Invoked Devastation, the Oeridians managed to save more of their great magical knowledge and profound lore than the Bakluni or Suel peoples did. The concentration on “combat magic” by Oeridian mages was ruthless and played a key role in strategic defeats of the Suel, with their subtler wizardry, in particular.
Initially, this powerful resource kept the Oeridians on top, but in the long run it stilted the creativity of their wizards—over-specialization leads to insights which are too few and of too limited application. Thus, both the dominance and the decline of the Oeridians can be seen in their wizardry.
The priesthoods of the Oeridians also played a vital role. Deities of travel, such as Procan, Celestian, and Fharlanghn supported their people’s restless drives to new lands. Zilchus’s priests played a key role in supplying, provisioning, and distributing resources and goods. The martial priesthoods of Heironeous, Hextor, and even Erythnul all had their role in driving on Oeridian armies.
The Heironeous-Hextor enmity actually drove the armies of different houses of Aerdi to greater struggles and competition for glory. Against the Suloise in particular, this combination of priesthoods proved highly effective. The Suel pantheon had few potent deities. Among only three intermediate powers, Lendor’s faith was a stagnant, wholly less creative one, and that of Wee Jas was too mystical, too fixed to lead active resistance to the Oeridians.
The evil Suloise deities too often failed to strengthen their people, but rather to conceal them at the margins, in the shadows, unable to oppose the strength of the Oeridians save by subversion and sabotage. Consider Pyremius and Syrul, for example; the are powers of lies, deceit, and poisonings.
Thus, the Suel people were easily driven like the wind before the wrathful Oeridian armies, marginalized to the boundaries of the Flanaess.
Carl Sargent. Greyhawk Adventures, Ivid the Undying, 1995