As Cryotek summons his power his helmet changes to red,
When the Spectral Knights are first standing on Shadow Mountain, Cryotek's helmet is red, before returning to normal in the next scene. Then a few moments later, as Leoric summons the Owl of Wisdom, Cryotek's helmet is red again.
When four of the Spectral Knights are captured by the Darkling Lords, Darkstorm orders his enemies' weapons and Power Staffs placed in the Magical Dungeon. It's clear that he intends to steal every bit of magic the Spectral Knights possess because he adds that the Magical Dungeon will also be used to remove their Totem powers. Trouble is, as far as the Visionaries' weapons are concerned, the only one known to have any magical properties is Feryl's dagger, and Feryl is not among those captured.