Couatl Familiar (Pact of the Chain)

Shapechanger. The couatl can use its action to polymorph into a beast form that resembles a lizard (speed 20 ft., climb 20 ft.), a poisonous snake (speed 30 ft., swim 30 ft), or a raven (20 ft., fly 60 ft.), or back into its true form. Its statistics are the same in each form, except for the speed changes noted. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Magic Weapons. The couatl's weapon attacks are magical.

Shielded Mind. The couatl is immune to Scrying and to any effect that would sense its emotions, read its thoughts, or detect its location.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: (1d4 + 3) piercing damage, and the target must succeed on a DC 11 Constitution saving throw or be poisoned for 24 hours. Until this poison ends, the target is unconscious. Another creature can use an action to shake the target awake.

Invisibility. The couatl magically turns invisible until it attacks, or until its concentration ends (as if concentrating on a spell). Any equipment the couatl wears or carries is invisible with it.