Severence Crook

In the Crystal caves I found a a Crystal which Kreia made a big fuss about, telling me how it was tuned to me and would help me out. So I go to equip it into my Lightsabre only to find that its Darkside only and my character is pretty much as lightside as possible. Now what the hell point is that? Surely if your playing the lightside route you should get a lightside version of the crystal and vice versa right? Also how the hell do I beat Kreia?