Here are a couple of Doppelgangers Priests of Deceit that my group ran into. They travel the land spreading chaos and confusion.
Darcous:
Doppelganger – 3rd level Priest of Deceit
Medium monstrosity (shapechanger) Chaotic Evil
AC: 16 (studded leather + dex)
HP: 8d8+16+3d8+6 (72)
Speed: 30’
Str: 12 (+1) Dex:18 (+4) Con:14 (+2) Int:11 (+0) Wis:16 (+3) Chr:12 (+1)
Skills: Deception +5 Insight +5
Condition immunities: charmed
Senses: Darkvision 60’, passive Perception 13
Languages: Common
Challenge 4 or 5 (1100xp or 1800xp)
Shapechange: see mm pg82
Ambusher: Advantage on attack rolls against any creature it has surprised
Surprise Attack: +3d6 damage on surprise attacks in the first round of combat
Multiattack – Can make two melee attacks with either:
Claws +6 to hit (1d6+4)
Finesse weapon +6 to hit (+4 damage)
Melee weapon +3 to hit (+1 damage)
Read Thoughts see mm pg 82
Spellcasting 3rd level cleric trickery domain
Spells per day: cantrips x 8 | 1st level x 4 | 2nd level x 2
Prepared Spells:
Cantrips:Thaumaturgy, Guidance, Mending
1st: Charm person(domain), Disguise self(domain), Command, Sanctuary, Cure Wounds
2nd:Hold Person and Calm Emotions,Silence or Enhance ability, Wording bond
Blessing of the Trickster – Touch other give advantage on dex stealth
Channel Divinity: Invoke Duplicity PHB PG 63
Jord:
(same as above except the following differences)
Doppelganger – 2rd level Priest of Deceit
HP: 8d8+16+2d8+4(65)
Challenge 4 (1100xp)
Spellcasting 3rd level cleric trickery domain
Spells per day: cantrips x 6 | 1st level x 3
Prepared Spells:
Cantrips:Thaumaturgy, Guidance, Mending
1st: Charm person(domain), Disguise self(domain), Bane, Command, Sanctuary, Cure Wounds, Inflict wounds.
They use their shapechange and Disguise self to quickly blend into crowds to escape trouble or Invoke Duplicity when retreat is necessary. They prefer surprise attacks and avoid combat unless they have an obvious advantage.