Thousands of years ago, a cruel, aquatic race called the kopru embarked on a mission of conquest and established a mighty undersea empire. The legendary might of these creatures was rivaled only by their cruelty to both enemies and subjects. The vicious kopru conquered and enslaved all the other sentient aquatic races with which they came into contact, including aquatic elves and sahuagin.
The aquatic elves who had not yet been enslaved by the kopru built their settlements far away from the empire’s borders, but still they lived in fear of its expanding army. Constantly fortifying their defenses, the elves watched and waited for the day when their enemies might attempt to annex their territory and enslave them.
The sahuagin had not yet reached the pinnacle of their power as a race, but their numbers were increasing, and those not already absorbed into the empire harried its borders on a regular basis, seeking to free their enslaved kin. An individual kopru could easily defeat a single sahuagin, but the sahuagin often overpowered kopru defenders by sheer numbers. However, even the clerics of the shark god Sekolah could not provide the sahuagin with the leadership they needed to overthrow their kopru oppressors.
At last, as the elves had feared, the kopru began expanding once again, pushing the borders of their holdings outward. The aquatic elves saw this expansion as a real and imminent threat to their continued survival, so they sought allies for a final stand. The elf leaders met in secret with the leaders of the various sahuagin factions and eventually formed what would be an effective but short-lived alliance.
Bolstered by elven magic and complex strategic planning, the sahuagin army moved against the kopru expansion forces. In a single week, the unlikely allies attacked and sundered one kopru outpost after another. The cost in sahuagin life was enormous, but still they persevered.
After the kopru incursion into elven and sahuagin territory had been repelled, the sahuagin wanted to continue the fight, and the elves were more than willing to lead them into battle. The campaigns went on for years, gradually forcing the kopru farther and farther back within their borders. In time, their empire was simply overrun. Their cities were reduced to rubble, their slaves were freed and added to the invading army, and their citizens were slaughtered wholesale by the bloodthirsty sahuagin. The few surviving kopru fled their ruined cities and went into hiding.
Once they had soundly defeated the kopru, the aquatic elves and sahuagin fell to bickering over whose contribution to the war had been more valuable. Their alliance fell apart, and in less than a year, the two races were once again sworn enemies. Though a number of sahuagin fought to retain unity within their own race so that it might take the kopru’s place as the dominant force of the deep, old rivalries quickly resurfaced and splintered the tribes, diluting their power.