The Pantheon made the only decision they could rightfully make when they chose to imprison the Old Gods. The death of Y’shaarj proved that trying to remove the others would only further endanger and possibly kill Azeroth’s world-soul — and that was the last thing the Titans wanted. But in imprisoning the Old Gods, the Titans inadvertently changed the course of evolution on Azeroth for good.
The Curse of Flesh
Although the Well of Eternity was essentially a wound, it was also a blessing to the creatures that roamed Azeroth’s surface. The mysterious, potent energies radiating from the Well fostered and hastened growth and evolution across the world. The titan-forged left behind to tend to the world helped shape and foster that life, but they weren’t immune from evolution themselves.
When the Pantheon was slain by Sargeras, Norgannon cast a spell that sent their spirits, and the last of their powers, to Azeroth. There, they inhabited the keepers that watched over the prisons of the Old Gods. Their arrival caused a great disturbance in the keepers, who didn’t realize what had happened. Yogg Saron took advantage of the disturbance, weakening his jailers and making an escape. From there, the Old God tainted the Forge of Wills with the Curse of Flesh.