This will actually be a bit easier as a good natured person because people are more willing to follow you.
First you will need to gain entry to the Temple of Shadows. It is located in Rookridge near the exit towards Oakfield. At the gate, there should be a guy in a black cloak with a quest; he may not appear until you get the Hero of Strength. His quest is to eat 5 crunchy chicks, which he gives you, in front of him.
Once you do that, go through the gate and down the stairs. Once at the bottom, go through the tunnel. The room you come to has a circle in the middle of the floor; this is where you need to bring people. Go back to town and get as many people who are willing to follow you and drag them back to the temple (it should have been added as a point in the Areas menu under Rookridge). Once they are in the circle, pull the lever at the edge of the circle near the back of the room. This should sacrifice any who are in the circle. There is a small chance they could have walked out of it but they normally don't.
If you have already done the mission to defend the Temple of Light, then you can no longer use the Temple of Darkness as you have killed their leadership.