Aranea

Shapechanger. The Aranea can use its action to polymorph into a humanoid form or into a giant spider, or back into its true form, which is a hybrid form. Its statistics, other than its AC, are the same in each form. Any equipment it is wearing or carrying isn’t transformed. It reverts to its true form if it dies.

Spider Climb(true or spider form only). The aranea can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Web Sense(true or spider form only). While in contact with a web, the aranea knows the exact location of any other creature in contact with the same web.

Web Walker(true or spider form only). The aranea ignores movement restrictions caused by webbing.

Spellcasting. The aranea is a 3rd-level spellcaster. Its spellcasting ability is charisma (spell save DC 12, +4 to hit with spell attacks). The aranea has following sorcerer spells prepared:
Cantrips (at will): light, minor illusion, dancing lights, resistance
1st level (4 slots): sleep, mage armor
2nd level (2 slots): darkness, gust of wind

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., 1 target. Hit: 5 (1d6 + 2) piercing damage and the target must make a dc 12 Constitution saving throw or be poisoned for the next minute. 

Web (True form and spider form only)(Recharge 5-6). Ranged Weapon Attack: +4 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 12 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).