The Demon’s Heart is a grotesque, pulsating organ encased in a jagged, obsidian-like shell with veins of molten lava running through its surface. The heart itself is a deep crimson, with a sinister glow emanating from within, suggesting a malevolent life force. The shell features intricate, demonic runes carved into its surface, glowing faintly with an eerie blue light, contrasting sharply with the fiery veins.