You *should* have won just by taking Petrus' left nut out of Attnam. My experiments in wizmode tell me you don't even need to be Mort's champion to get that ending. However, since that's not happening, and you have killed Oree, you can try to get the high priest ending instead. This requires:
1. The Shirt of the Golden Eagle
2. Petrus' nut.
3. That you are Valpurus' champion.
4. Once you have the above three, all that's left is to sit on the throne that Petrus used to own.
Third part's likely going to be hardest since you became Mort's champion first, though if you're strong enough to kill Petrus it probably isn't going to be *terribly* hard to figure out a way to pull it off. BTW, if you succeed at this ending, you'll get a 4x multiplier on your score as opposed to the 2x multiplier you would have gotten with the Chaos ending.