The light question was already covered in the video posted earlier today, and subsequent breakdown of images from it. One of them shows the cursor scrolling over the light stat, and it says it increases both the overall attack and defense. They'll probably cover the info again in the podcast, but if you want to check out the details now, here's a link: http://www.polygon.com/2015/8/18/9172473/destiny-the-taken-king-year-two-teaser