The player soon comes under attack from Creatures of Darkness that appear out of nowhere and seem to be living shadows. These Creatures of Darkness are eventually revealed to be reptilian, silicon-based life forms from the center of the Earth, an enormous world of dark caverns known as the World of Darkness. Shadow Island apparently contains one of the many portals to this underground world. True to their name, the game's enemies are averse to light (which apparently turns them into ash), and this figures heavily in gameplay. Players can use their flashlight to repel certain creatures, and killing them is accomplished with such light-producing ammunition as "magnesium bullets" and "phosphorus shells."