Unraveler

Eternal Servitude. As a full-action, the unraveller can revive a CR 5 or below undead creature that have been slain within the last 24hours. The revived undead creature is restored to full health upon reviving.
All undead risen by this abillity are turned to dust upon the death of the unraveller who raised them.

Nasty Unbirth. When the unraveller dies, summon 1 Swarm of Poisonous snakes where it dies.
The Swarm counts as an undead, and gets a free attack against all creatures around it the instant that it is summoned.

Spellcasting. The unraveller is a 5th-level spellcaster. Its spellcasting ability is Wisdom (spell save DC 15, +4 to hit with spell attacks). The unraveller has the following cleric spells prepared:

Cantrips (at will): guidance, thaumaturgy

1st level (3 slots): bane, inflict wounds, command

2nd level (3 slots): hold person, silence, blindness/deafness

3rd level (2 slots): stinking cloud, animate dead

4th level (1 slots): polymorph

Multiattack. The unraveller can use its Dreadful Glaive-Hand twice and makes one attack with its rotting breath or unholy bolt.

Rotting Breath. Breath Attack: +3 to hit, reach 10 ft. cone , multiple targets. Hit: 10 (2d6 + 4) poison damage plus 10 (3d6) necrotic damage. If the target is a creature, it must succeed on a DC 14 Constitution saving throw at the start of its turn. If failed, it will take additional 1d4 poison damage and 1d4 necrotic damage. If the creature succeeds such a, it becomes immune to this attack for 5 rounds.

Dreadful Glaive-Hand. Melee Attack: +6 to hit, reach 5 ft., one target. Hit:  8 (2d6 + 2) piercing damage. 

Unholy Bolt. Missile Attack:  13 Dexterity save to avoid, reach 60 ft. long 5 ft. wide line, all on line is targets. Hit: 6 (1d12 + 1) necrotic damage. If the target is undead, they are hit automatically and heal 2d8 instantly, and nothing else. If the targets is a not an undead, it must succeed on a DC 13 Wisdom saving throw at the start of its turn. If failed, it will be paralyzed until its next turn. If the creature succeeds such a, it becomes immune to this attack's paralysing effect for 24 hours.