Thats why turtle seems to be so unchanged by his magic cause he only did things for the greater good, (not like darkstalkers greater good witch is only good to darkstalker) to help people in need of it
Theory:
Animus magic doesn't eat your soul. It's the fact that the more you use it, the more power you realize you have, therefore corrupting your soul with the thought of such power, and animus magic had nothing to do with all of this, it was solely the own dragon's fault. THINK ABOUT IT.