All of the spyder-fiends looked like some variation of a giant spider with a wolf-like head. The smallest spyder-fiends, the kakkuu, were about the size of a pony, being 5 feet (1.5 meters) long and weighing about 300 pounds (140,000 grams), while the largest spyder-fiends, the raklupis, were 10 feet (3 meters) long and weighed about 450 pounds (200,000 grams). Some of the spyder-fiends possessed arms in addition to their eight legs, including the phisarazu, lycosidilith, and the raklupis; spithriku possessed pedipalps. They were typically covered in coarse, dark or sandy brown hair with splotches of other colors, while the fur on the head was grey.
The fur of phisarazu was largely black, some with a blue or green tint, and swirled, striped, and/or spotted with different shades of blue, green, or grey. Lycosidiliths, by contrast, were largely hairless, instead being covered in green or blue chitin with speckles, spots, and/or rings of black, orange, and yellow. Raklupis also lacked fur on their spider bodies, but had a triple row of sharp spines on their back and black or grey fur on the head; the chitin and spines could be almost any color and were always vividly marked with swirls, bands, and spots of contrasting colors.
The spyder-fiends had several abilities in common, including infravision, a venomous bite, and the ability to produce silk, with which they could do several things, including binding opponents and catching themselves while falling. They possessed two spell-like abilities, darkness 15' radius and teleport without error. They were completely immune to damage caused by poison, electricity, and nonmagical fire, and were resistant to that cause by magical fire, cold, and poisonous gas.
Spyder-fiends were tanar'ri who combined the worst aspects of spiders and wolves. The less intelligent had all the charm of rabid, bloodthirsty wolves, while the more intelligent were manipulative and even eloquent. All were cunning and cruel.
The spyder-fiends were the servants of Miska the Wolf Spider, the second Prince of Demons, and by extension they served his lover, the Queen of Chaos. In fact, some sages speculated that the original spyder-fiends were the offspring of those two. They continued to serve the Queen of Chaos even after their master was locked away.
Circa 1362 DR, several spyder-fiends were under command of Cyric who tasked the creatures to nightly torment Kaverin Ebonhand as part of the payment for his resurrection. The sulfurous demons visited the leader of the Cult of Frost as he fell asleep and whispered horrors of torture eternal into his ears giving him restless sleep filled with nightmares. The creatures glade accepted "gifts" of dead bodies, dragging them to Cyric's realm for some nefarious reason. After Kaverin's second death at the hands of Artus Cimber, Cyric's spyder-fiends arrived to he Prime Material Plane for the last time, to claim Ebonhand's body and should, dragging him towards his eternal torture.
In 1371 DR[note 1], spyder-fiends were among the army of fiends that flooded the streets of Eldrinpar of Doegan in attempt to seize one of the Utter Easts bloodforges, shortly after the death of Aetheric III, the emperor of Doegan at the hands of Artemis Entreri.
- The Abduction, p.6 states that the wedding of Piergeiron the Paladinson and Eidola took place in the Year of the Haunting, 1377 DR. However, that date is implausible. Khelben Arunsun died in 1374 DR as depicted in Blackstaff (novel). Furthermore, Aleena Paladinstar was stated to be gone from Waterdeep by 1372 DR, planeswalking (City of Splendors: Waterdeep). On the other hand, the events of the Descent to Undermountain took place in 1370 DR, during which Aleena was actively banned from adventuring and any danger by her father. In the events of The Paladins, as well as the finale of the DDTS, Aleena took a central role, no longer bound by her father's rules. She later, with all the experience she received from battling the Unseen and hordes of Tanar'ri, felt confident enough to use her magic to traverse the planes. This places DDTS events likely in 1371 DR. This also does not conflict with appearances by Artemis Entreri, and the Neshers.
- Skip Williams (1996-09-02). “Book IV: Monsters”. In David Eckelberry ed. The Rod of Seven Parts (TSR, Inc.), pp. 7–12. ISBN 978-0786904181.
- (1998). Monstrous Compendium Annual Volume Four. (TSR, Inc), p. 76. ISBN 0-7869-1212-X.
- James Lowder (November 1992). The Ring of Winter. (TSR, Inc), chap. 16, p. 297. ISBN 978-1560763307.
- Eric L. Boyd, Ed Greenwood, Steven E. Schend (2000). Presenting...Seven Millennia of Realms Fiction. Wizards of the Coast. Archived from the original on 2003-06-21. Retrieved on 2015-08-12.
- J. Robert King (April 1998). Conspiracy. (Wizards of the Coast), p. 56. ISBN 0-7869-0869-6.