Marshadow resembles a shadow and has a wispy figure. It is predominantly black and seems to be wearing some sort of helmet. The helmet has two horn/ear-like appendages with a wispy smoke in the center. Its eyes are orange-red with an oval on top. Its arms possess a bump on each wrist. Marshadow appears to wearing a collar and its legs have a shadowy trail. It has a tiny mouth.

As Zenith Marshadow, its headgear, bumps and collar flare up with green yellow flames, and its eyes also flare up.