When you head up the path to the monastery you will see dead body that look mostly eaten about 5 miles up the path ( party * 10.) When you pass they will make a gurgling noise. Shortly after they will stand up and attack the party. When they die a Baby will crawl out of the ground and raise them. When you kill The necromancer all the thrall will die. There will be more half eaten body all over the path along with other animals. The DM rolling a natural 20 will result in the same thing with an animal. 1-5 bear * 1d4 6-10 lion * 1d6 11-15 giant slugs * 1d10 16-20 is ogres * 1d20.