Majesto

Majesto can use its action to polymorph into a beast form that resembles a rat (speed 20 ft.), a raven (20 ft., fly 60 ft.), or a spider (20 ft., climb 20 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.

Magical darkness doesn't impede Majesto's darkvision.

Majesto has advantage on saving throws against spells and other magical effects.

Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 3) piercing damage, and the target must make a DC 11 Constitution saving throw, taking 10 (3d6) poison damage on a failed save, or half as much damage on a successful one.

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

Imps can be found in the service to mortal spellcasters, acting as advisors, spies, and familiars. An imp urges its master to acts of evil, knowing the mortal's soul is a prize Majesto might ultimately claim. Imps display an unusual loyalty to their masters, and an imp can be quite dangerous if its master is threatened. Some such imps have the following trait.

Familiar: Majesto can enter into a contract to serve another creature as a familiar, forming a telepathic bond with its willing master. While the two are bonded, the master can sense what Majesto senses as long as they are within 1 mile of each other. While Majesto is within 10 feet of its master, the master shares Majesto's Magic Resistance trait. If its master violates the terms of the contract, Majesto can end its service as a familiar, ending the telepathic bond.