Shadow asps were 4‑foot-long (1.2‑meter) serpents with dark, patternless scales, which made them difficult to see in shadows. They often appeared slightly translucent.
Although smarter than most nonmagical snakes, shadow asps were still beasts that acted on instinct.
Shadow asps, as magical beasts, possessed a few nasty magical surprises. They could become incorporeal at will for up to an hour every day. They were also venomous, and any creature slain by their venom would rise as a shadow within two days, uncontrolled but bound to the location they died in as a guardian, unable to move more than 100 feet (30 meters) away from where they rose.
Shadow asps preferred to attack by becoming incorporeal, then emerging from the walls, floor, or ceiling en masse to bite potential prey, then retreating to let their venom take effect. They were often accompanied by the shadows their venom created.
Shadow asps were thought to have originated on the Plane of Shadow, but were often found on the Material Plane in dungeons and tombs, as their venom made them useful guardians of such sites. They were also found near portals to the Plane of Shadow and in remote locations in the Underdark. They were naturally both watchful and quiet, and lived either alone or in clutches of three to twelve shadow asps.
- Eric Cagle, Jesse Decker, James Jacobs, Erik Mona, Matthew Sernett, Chris Thomasson, and James Wyatt (April 2003). Fiend Folio. (Wizards of the Coast), pp. 152–153. ISBN 0-7869-2780-1.
- Ed Greenwood, Eric L. Boyd, Darrin Drader (July 2004). Serpent Kingdoms. (Wizards of the Coast), p. 5. ISBN 0-7869-3277-5.