Most creatures have human-visible light spectrum vision, but some have other forms of sight, often in addition to the visible light spectrum. The three exotic forms of vision are given below:
Infrared-Also known as “heat vision,” Infrared allows creatures to see according to heat, easily identifying a living being from a wall, but perhaps not being able to tell the difference between a wall and a door, or a statue and a zombie. Infrared vision is possessed by creatures that dwell in some of the deeper dark areas, including dwarves, orcs, kobolds, lizard men, and dark elves.
Ultraviolet-Just past the high frequency end of the visible light spectrum, ultraviolet, or “low-light,” vision allows creatures to see at a wider band of light, allowing vision in darker conditions than humans can normally see. It is possessed by creatures that are active at night or that live in shallow caves, including elves, hobgoblins, and bugbears.
Echolocation-Some creatures can travel by sound by emitting a high pitched sound and hearing its echoes. These creatures are usually large eared and live in very deep caves where their is little or no light; they include gnomes and goblins. Using echo-location belies attempts at stealth and shows only rough shapes.