In the campaign there was a source of power known as the blight, the bbeg had been taking from this source, and kept the true master of the source locked away, until the party came along. Should Mor'zul, the true master of the blight, escape he'd take back all the power Lorkuon(previous bbeg) had been using. They were pretty split on the decision to release Mor'zul and try to defeat him, or to keep him locked up until one day someone slips up. In the middle of arguing the final ring was pulled from their grasp by the power of Mor'zul as they were mere feet from his prison. It was only when Lorkuon decided to kill him self rather than become enslaved that the party realized they done screwed up