Black Widow

Neurotoxin. The Black Widow's bite is especially poisonous. if a creature fails its con save against the black widow's bite its speed is halved and it cannot take the dash or dodge actions while poisoned

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: +4 to hit, reach 5 ft., one creature. Hit: 1 piercing damage, and the target must succeed on a DC 9 Constitution saving throw or take 2 (1d4) poison damage and be poisoned for 10 minutes