User blog comment:Xilinoc/Ch. 582 - The Headless Star/@comment-24994192-20140528100926

My personal guess for Askin's power is "the Darkness" Two reasons for this:

1. when first introduced in the chapter 543 he stepped out of a dark portal in mid-air rather then just being shown like the others.

2. after showing up in chapter 547 in Maiyuri's lab, he explains how the Vandenreich stayed hidden for so long: using the shadows to conceal themselves within the soul society itself. possibly a hint at him knowing how this is accomplished

We have seen that the "shadows" are just another form of spirit energy, so maybe he can personally manipulate them the same way Bazz-B can manipulate heat

Just my two cents on him