It may have been dark magic that created you, but the notion that darkness is suited only for evil ends is a misconception. I am an incomplete being as well, though it was my heart excised from my body, rather than my soul.

[He taps his chest, right where his literal heart would be.]

The important thing is to remain true to yourself. Even if the dark magic has left a mark on your soul, don't allow it to define you, but don't fear it, either. Fearing something grants it power over your heart, which is where the danger truly lies.