Cherub

Shapechanger. The Cherub can use its action to polymorph into a beast form that resembles a mouse (speed 20 ft.), a dove (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.

Angel's Sight. Magical darkness doesn't impede the Cherub's darkvision.

Magic Resistance. The Cherub has advantage on saving throws against spells and other magical effects.

Variant: Familiar: The Cherub can serve another creature as a familiar, forming a magic, Telepathic Bond with that willing companion. While the two are bonded, the companion can sense what the Cherub senses as long as they are within 1 mile of each other. While the Cherub is within 10 feet of its companion, the companion shares the Cherub's Magic Resistance trait. At any time and for any reason, the Cherub can end its service as a familiar, ending the Telepathic Bond.

Friends: The Cherub can cast the friends cantrip, but gives it's master the advantage.

Lay on hands: The Cherub has the level one ability of lay on hands. 

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