Awakened Spider

Spider Jump. The Awakened Spider's jump is 300ft.

Spellcasting. The Awakened Spider can cast darkness three times a day.

Tetrapodal Crawl. The Awakened Spider readjusts into a more spider-like form. While in this form, it has a base movement speed of 60ft. Until its next turn, it has immunity to fire and non-magical slashing, bludgeoning, piercing, and resistance to all damage. It may take action to return to its bipedal form.

Multiattack. The Awakened Spider makes two Arachnid Stab attacks. If it's in its bipedal form, it may replace one of the Arachnid Stab attacks with an Infectious Bite Attack.

Arachnid Stab. Melee Weapon Attack: +6 to hit, reach 5 ft., 1 target. Hit: 7 (2d4 + 2) piercing damage. 

8-Legged Stampede (Tetrapodal Form only). Melee Weapon Attack: +8 to hit, range 5 ft., 1 target. Hit: 12 (2d6 + 5) bludgeoning damage and an additional 7 bludgeoning damage if it moved at least 15 ft this turn. A creature is sent flying 5 feet away.

Infectious Bite (Bipedal Form only). Melee Weapon Attack: +6 to hit, range 5 ft., 1 target. Hit: 6 (2d4 + 1) poison damage. A creature hit by this must make a DC 12 Constitution saving throw or be infected with a disease. The disease gives the victim vulnerability to poison from venomous arachnids and removes 1d4 max hp from the victim every dawn. At dawn, the victim may make a DC 18 constitution saving throw to remove the disease.