Leon thought he would feel something annoying after torturing the terrorists, but he didn't feel anything. He didn't feel good, nor did he feel bad. In the end, he felt satisfied with that. It was a sign that his psych wasn't that damaged.
After making an example out of the first terrorist, Leon still burned one of the legs of the other ones. Causing damage without asking anything first was an excellent way to convince them to talk. Unfortunately, in the end, Leon only obtained a few pieces of information. First of all, they never met the harvester who was controlling them. The sneaky bastard only talked directly with their minds and gave them directions. Upon arriving in those places, the terrorists obtained magic items and tomes. They used that to get stronger and become the leaders of small groups of survivors. Now and then, they would hear the voice of the harvester promising them more tomes and magic items... as long as they cause a ruckus on Earth.
