Fiendish Resistance. The Abyssal spider due to its fiendish nature makes all saving throws vs. blindness attacks at advantage.

Spider Climb. The spider can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Web Sense. While in contact with a web, the spider knows the exact location of any other creature in contact with the same web.

Web Walker. The spider ignores movement restrictions caused by webbing.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 10 (1d8 + 6) piercing damage, and the target must make a DC 13 Constitution saving throw, taking 9 (2d8) poison damage on a failed save, or half as much damage on a successful one. If the poison damage reduces the target to 0 hit points, the target is stable but poisoned for 1 hour, even after regaining hit points, and is paralyzed while poisoned in this way.

Hypnotic Stare (Recharge 5–6). During any round the spider has this attack recharged, as a bonus action the spider will chose a random target within 30' feet for this attack.  When that target begins their turn the creature will have to make a DC 13 Wisdom saving throw or be hypnotized by a swirling color pattern in the spider's eyes.  The hypnotized creature will simply stare into the spiders eyes until their next turn losing their ability to take any action or bonus action until their next round.  This hypnotic state will not imped the target's reaction, just their actions and bonus actions for that one round.

Web (Recharge 5–6). Ranged Weapon Attack: +6 to hit, range 30/60 ft., one creature. Hit: The target is restrained by webbing. As an action, the restrained target can make a DC 14 Strength check, bursting the webbing on a success. The webbing can also be attacked and destroyed (AC 10; hp 5; vulnerability to fire damage; immunity to bludgeoning, poison, and psychic damage).