What is \"evil\"?

As Abraham Lincoln once said, \"The true rule, in determining to embrace or reject any thing, is not whether it has any evil in it; but whether it has more of evil than of good. There are few things wholly evil or wholly good. Almost every thing ... is an inseparable compound of the two; so that our best judgment of the preponderance between them is continually demanded.\"

Everyone has a little bit of evil in them, some people just have more.

Is there any difference between a Fire short sword and an Icy or Dark one. If you have more Dark way magic, will a Dark sword do more damage, or what will this do?  Or specific strengths and weaknesses betweeen the different elemental swords?