The Ssatrekis is the name given by the Kaaradi to a species of gigantic spiders, which is one of the two apex predators of the Kaarad, the other being the Bilious Wyrm. Those huge spiders doesn't use a lot of poison, using surprise and their enormous strengh to hunt their prey.
Melkor morgoth vs ungoliant by jossand-d4mso3r

A Ssatrekis and its prey; Art by Jossand

The Ssatrekis, while enormous has a very flexible body, and it can compress its belly, which allow it to hide in narrow cracks, which seem far too little to hide for such a huge beast. It doesn't produce spider web and trap they prey, usually from the above, thanks to their powerful legs which end with a huge claw like extremity. The Ssatrekis are totally blind and detect their prey thanks to very sensitives organs around their legs, which allow the spider to feel the reverberation produced by the feet of its prey while they move. Furtheremore, the Ssatrekis have other organs near its vestigial eyes which allow it to detect the shitf in air pressure (while they are indetectable by most of the living creatures) induced by its prey movements.

The Ssatrekis are solitary creatures, except during the mating season (which last roughly one month), when males will try to impress females by bringing large prey (which could sometimes be weaker males) and offering them to the female. During this season, both the males and females are a lot more aggressive than usual, which is induced by the fact that both males and females need to eat a lot more then usual to survive the mating process.

Indeed, during the mating, the male and the female wrestle each other, with the former seeking to flee the latter since female Ssatrekis sometimes eat weaker males as a mean to gather energy for the laying. Usually, however, the male manage to escape, even if he could be maimed for some times (those who survive two months will undergo a metamorphosis where their maimed legs will regrowth).

After two month of maturation, the female lay ostrich-size eggs (between twenty and thirty) and leave them alone. When the newborns Ssatrekis go out of their eggs, they will enter a frenzy of cannibalism, eating each other until only five to ten survive. The survivors will then scatter to the four winds. The first year is the most dangerous one, since the newborn have to eat a lot but are too little to hunt big prey and their chitin isn't thick enough to protect them; their only weapon is their poison, which is a lot more potent than the adult's one. Usually, only one newborn Ssatrekis survive to see its first year coming to an end. Those which do, however, are already deadly predators, roughly the size of a tiger after a series of metamorphosis. However, it still lack the claw like extremity at the end of its legs, which will appear at the age of two.

A Ssatrekis is sexually mature at the age of four and usually die at the age of thirty