How to get the evil purple robe?

The purple cassock is on the fluorescent crow in the stone at the upper left of the black lake. Kill it, and it will fall. Only by reaching the realm of preaching can you become a purple-robed Taoist. The color of the vestment represents different meanings: purple vestment: written by a master, or a Tianshi or a senior mage. Red vestment: written by a senior mage and used for prayer on the table.