Priest Adonius:
Unlike your gods, who hide truth within darkness, Einhasad is a benevolent god. We priests have been permitted a portion of the songs of light, written in Andariel's Book. If you have decided to repent your wicked past and follow the creed of the light, I will give you a copy of the ancient book.
Atonement is not that easy. If you go east of here to the Ruins of Despair, there are many undead that cannot rest in death. To destroy these undead, you must send the good spirits still trapped inside them into the arms of Einhasad. If you bring back ten Ashen Bones that can be obtained by killing the skeletons or zombies in the Ruins of Despair, you will finish your atonement ritual.