Darkweaver's had his mark from Osias and it's side effect for well over a year now, but I've still never drawn it's effect in action until now.
Essentially, whenever he moves his body takes on a shadowy appearance, losing it's pigmentation progressively as he moves faster. At a run or full gallop all that remains of his stationary visibility is the red of his eyes.
Further, when asleep he may go into a 'shadow walking' state where his spirit, strength, and conscious mind separate from the body and may act as he might while awake, still interacting with the world as a 3D shadow, keeping the red eyes. Of course, in this state he will remain appearing as only a shadow when standing still. What differentiates his real body and his 'shadow/shadow walk' to an onlooker is the lack of chains on his legs in the later form. When awake, he'll still have his shackles.
Pardon the title. I couldn't think of anything fitting. So have a Doctor Who quote.