Body length (excluding legs) of adult female ranges from 0.9-1.2 m; adult males range from 0.6-0.9 m.
These spiders seem to be built for speed and, with the help of dense brushes of hairs (scopulae & claw tufts) on the last two segments of their legs, they can easily maneuver walls and ceilings with ease. In relation to body size, their legs are not very long, but are strong and thick, especially in the adult females. All legs are noticeably velvety or hairy-looking, more so in adult specimens, and are a solid brownish-orange color. Unlike web-building spiders, which usually have three tiny claws on the very tip of each leg, this hunting species only has two claws.
Both genders are very similar-looking. The body of this species is somewhat slender and flattened, with the cephalothorax and abdomen essentially equal in size. The carapace is the same color as the legs, brownish-orange, and is covered in reflective silvery hairs. The elongated abdomen is dark gray and appears velvety and soft, reminiscent of a mouse. Even from a distance, one can see how furry the spider looks. The long, cylindrical “tail-pipe” spinnerets help to peg it as a member of the family Gnaphosidae.
This is a nocturnal hunting spider that does not spin a web to catch prey; it hunts “on foot” instead. It uses its silk for other purposes, such as safety lines, egg sacs, and little silken daytime retreats. Incidentally, we have noted in our observations that the “chamber” of webbing created around the egg sac is actually a pretty extensive labyrinth of silk
Prey is any insect or other spider it is able to chase down and subdue. Scotophaeus blackwalli is very fast and can climb walls and ceilings with ease, which makes it quite a skilled and agile predator. Each time the spider bites it will also inject venom. This venom acts quickly. It is a Dex-8-10 venom. This means after 10 action rounds, the Venom will reduce Dex by 5. This amount is reduced by a Con roll. Each Ss reduces the damage to Dex by 1. The next 10, by 4, the next 10, by 3 and so on until either Dex is 0 or the Potency is 0.