Immolation
You can feed off the weak if you are willing to walk the path of power. Find a victim who trembles before you and simply sacrifice his body and soul for your own personal strength. By harnessing that tortured soul through the immolation, you can use it to boost the strength of your damage spells for a period of time. The spirit doesn't mind... much. A little afterlife pain is an enlightening experience for them.
Prerequisite(s): Demonic Intent.