Lights are visualized in the story as grotesque creatures with inhuman strength and speed. Although, unlike other undead creatures, Lights only kill and not eat. Their diet consists of vegetables and anything non-human; they do not like human flesh for a mysterious reason. Lights are also immune to fire and somehow ironic, afraid of light. Any form of light will scare them, but will depend on what stage they're in.
Lights are shown in the book with various stages in their lifetime because of the prolonged effects of the NLV (Northern Light Virus). In cases, this is referred to as the Light ladder.
Stage 1: Glares
Glares is the first stage of the basc Light ladder. In some stories, this is known as the "turning" point where the virus overtakes the human body. The body of a Glare is in between the full-Light and the human body and is feared in the world of Our Last Days because they can walk in sunlights. Symptoms are dazed expression, walking dead in the sunlight, sluggish movement, though mainly caused by the infected resisting the virus. Aside from that, when provoked, a Glare will lose control and instantly retaliate to the provoker. Transition from a human to a Glare is between the time when the human is infected and the time when he or she becomes a full Light, and during this transition they maintain some humanity in them, though slowly degrading as time passes. The time needed to complete the transition is in the average of 3 days. In 3 days of being a Glare, the human will undergo the full transition into a Light.
Stage 2: Lights
Light is the second stage of the basic Light ladder. This is the most common form a Light can take. At this stage, the Light undergoes major adaptations such as: long, sharp nails which they use as claws; improved speed and agility; and brute strength. Lights only comes out at night when any light source is extinguished. Ironically, they are afraid of any light source and will stay clear when light shines upon them. Lights are more feral and aggressive than Glares, as this stage eliminates all human thinking, memory, emotion and instinct, and when they spot a nearby uninfected, they will attack mercilessly without hesitation. Lights can be found roaming inside buildings or areas with no light source during the day, but at night they roam all around in sheer numbers, using their heightened sense of smell or hearing to find prey. Despite their predatory instincts, they do not intend to kill humans to eat them, but only to kill them.