The Black Soul Gem is a dark, ominous crystal with a jagged, irregular shape, resembling a fractured piece of obsidian. Its surface is smooth yet subtly textured with faint, swirling patterns that seem to absorb light, giving it a matte, almost void-like appearance. The gem emits a faint, eerie purple glow from within, suggesting its cursed nature and its capability to trap souls. Its proportions are roughly the size of a human fist, with sharp edges and a weighty presence that feels both ancient and malevolent.