This is the fourth (and probably final) part of Age Before Ages: D&D Ancient History.
Dungeons & Dragons Fourth Edition breaks some continuity with the old Greyhawk-based history and takes its own setting. Nevertheless, the broad strokes of pre-history are the same. The gods fought with primordial beings long before the time of men, and in the end the gods won. Mythical figures like the Miska the Wolf-Spider and the Wind Dukes of Aaqa still appear on the correct sides.
According to the 4th edition Dungeon Master’s Guide 2, the Wind Dukes were a group of seven angels who served Bahamut, and forged the Rod of Seven Parts with the assistance of one of Moradin’s exarchs. The rod hates all elementals (strange since in 3E the Wind Dukes were elementals), strongly hates primordials (a term which doesn’t exist in 3E), and defends immortals (including demons, such as Miska the Wolf-Spider).
This isn’t actually too far from the 3E myth. According to Dungeon’s Age of Worms series, armies of evil elementals fought on the side of Chaos at the Battle of Pesh, including the earth elemental prince OgrÃ©moch. One hypothesis is that the oldest gods already existed at this time, and several fought on the side of Law, in which case it’s likely that the Moradin, Bahamut and a group of Wind Dukes collaborated in secret on the construction and deployment of the Rod of Law.
It’s feasible then that the Rod has a mild hatred of elementals, who mainly took the side of Chaos, and is somewhat protective of immortals, who aided its creation. It devotes itself to destroying the remaining primordials, whose number may include most of the surviving leaders from the side of Chaos. Although the Rod should hate demons, perhaps it has a strange tolerance of the tanar’ri, who overthrew the primordial obyriths after the battle, and thus in the grand scale of things tilted the balance of power against Chaos.
On the surface, it’s a little confusing that the Wind Dukes, who are air elemental creatures, would create a weapon that hates elementals. One possible answer is that the Wind Dukes were in fact created by the gods, in a time before any mortals existed whose souls could be forged into new beings; instead, they used elemental air to create intelligent beings to fight on the side of Law. This would strengthen the idea that the early conflict of Law versus Chaos was closely linked to the conflict between Gods and Primordials.