Cassiel the Oathbound

Spellcasting. Cassiel is an 11th-level spellcaster. Her spellcasting ability is Wisdom (spell save DC 15, +7 to hit with spell attacks). She has the following Cleric spells prepared (7 spells known):
Cantrips (at will): Light, Spare the Dying, Thaumaturgy, Word of Radiance, Mending

1st level (4 slots): Cure Wounds, Guidance, Sacred Flame, Command

2nd level (3 slots): Hold Person, Lesser Restoration, Prayer of Healing

3rd level (3 slots): Protection from Energy, Revivify, Magic Circle

Potent Cantrips. Cassiel can add its spellcasting ability modifier to the damage it deals with any cantrip.

Spell save DC = 8 + sidekick’s proficiency bonus + spellcasting ability modifier (15 at 11th level)

Spell attack modifier = sidekick’s proficiency bonus + spellcasting ability modifier (+7 at 11th level)

Multiattack. Cassiel makes two Maul attacks

Maul. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) bludgeoning damage plus 10 (3d6) radiant damage. 

Healing Hands. (4d4) As an action, you can touch a creature and roll a number of d4s equal to your proficiency bonus. The creature regains a number of hit points equal to the total rolled. Once you use this trait, you can’t use it again until you finish a long rest.

Channel Divinity: Turn Undead. As an action, you present your holy symbol and speak a prayer censuring the undead. Each undead that can see or hear you within 30 feet of you must make a Wisdom saving throw. If the creature fails its saving throw, it is turned for 1 minute or until it takes any damage. A turned creature must spend its turns trying to move as far away from you as it can, and it can’t willingly move to a space within 30 feet of you. It also can’t take reactions. For its action, it can use only the Dash action or try to escape from an effect that prevents it from moving. If there’s nowhere to move, the creature can use the Dodge action.

Radiant Soul. Two luminous, spectral wings sprout from your back temporarily. Until the transformation ends, you have a flying speed equal to your walking speed, and once on each of your turns, you can deal extra radiant damage to one target when you deal damage to it with an attack or a spell. The extra damage equals your proficiency bonus. Your transformation lasts for 1 minute or until you end it as a bonus action. Once you transform using your revelation below, you can’t use it again until you finish a long rest.