Steeder

Steeders are giant spiders which live in the Underdark, sharing many physical characteristics of their smaller cousins. Their bodies were covered in a fine fur that varied in color. They had eight powerful legs and large mandibles.
A common tactic used by duergar cavalry was to ambush a target and charge in, using the steeder's mass to smash a target against a wall or push them over a cliff. Steeders instinctively used their mandibles to bite a target.
Thanks to their strong legs, steeders are excellent jumpers. They are capable of leaping 24‒30 ft (7.3‒9.1 m) in any direction. They are also able to survive a drop of up to 24 ft (7.3 m). It was originally reported steeders lacked a venomous bite, but later accounts stated they did have one. Steeders have the innate ability to duplicate the effects of the invisibility spell once per day, which also affected their duergar rider. Steeders can walk on ceilings and walls using a sticky substance secreted from the base of their legs.
Steeders are predatory and aggressive, even to one another. A steeder would instantly attempt to attack another steeder. Due to this, they are stabled in individual stalls and blinders are used when more than one steeder is used in a caravan or battle group. Steeders are capable of being trained to respond to both hand and verbal commands.
Steeders were domesticated by the duergar and employed as mounts.Female steeders are used in battle while the smaller males are used to transport cargo. A steeder was able to transport between 300‒900 lb (140‒410 kg) of cargo or equipment. Unlike other dray animals, steeders would not pull a wagon; A duergar rode on the back of the steeder in a specialized saddle made from leather. Connected to this saddle is a complicated system of prods and straps, which allowed the duergar to control and direct the steeder.
There is demand for steeder eggs, with an individual egg fetching up to 500 gp at the market.  Steeders have to be properly trained and a steeder trainer was considered a professional trade among the duergar. An experienced steeder trainer could charge up to 1,000 gp for their services.
Female steeders are both larger and stronger than males. They tolerated each other during mating, but afterwards the female devoured the male. Once hatched, a newborn steeder reaches maturity within six months. Steeders are obligate carnivores. Steeders were selectively bred by the duergar from giant hunting spiders that were common in the Underdark. As a result, steeders are far more intelligent than their ancestors.
Source: https://forgottenrealms.fandom.com/wiki/Steeder