Bone Cleric

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

Blood feast. Anytime bone cleric deals melee damage to a living creature, the bone cleric recovers HP equal to half of the damage, rounding down.

Sickened bones. When grappled or grappling, the target takes 1d4 piercing damage initially. If the target starts its turn grappled, it must succeed on a DC 17 Constitution saving throw or take 4d4 poison damage.

Innate Spellcasting. The bone cleric's spellcasting ability is Wisdom (spell save DC 19). The Spell Sword can innately cast the following spells, requiring no material components:

At will: dancing lights

1/day each: cloudkill, insect plague

3/day each: hold monster

4/day each: animate dead

Multiattack. The bone cleric makes two attacks with any combination of its claw or poison spikes.

Claw. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) slashing damage + 15 (3d6 + 5) necrotic damage. A target that has been clawed can be grappled with advantage by the bone cleric as a bonus action, unless it is already grappling another target.

Life Drain. A grappled target must succeed on a DC 18 Constitution saving throw or take 21 (6d6) necrotic damage, and the bone cleric regains hit points equal to the total damage dealt. The creature's hit point maximum is also reduced by an amount equal to the damage taken. The target dies if this effect reduces its hit point maximum to 0. This reduction lasts until a creature finishes a long rest.

Poison Spikes. Ranged Weapon Attack: +6 to hit, range 60 ft., one target. Hit: 4 (1d4 + 2) piercing damage + 10 (3d6) poison damage.

Bone Shriek (Recharge 6).  The bone cleric makes a deafening, high-pitched scream. All creatures within 90 feet of it must succeed on a DC 20 Constitution saving throw or take 21(6d6) thunder damage and become deafened for 1 minute. A target that makes its save takes half damage and is not deafened. Grappled targets that fail their save also become stunned until the start of their next turn. If a target is killed by this damage, its head explodes, assuming it has one.

Nightmare Darkness. (Recharge 6 after the effect ends) Magical darkness spreads around the bone cleric, filling a 60-foot-radius sphere for 2 minutes or until the bone cleric is killed, knocked unconscious, or decides to end this effect. The darkness spreads around corners. A creature with darkvision can’t see through this darkness. Nonmagical light, as well as light created by spells of 5th level or lower, can't illuminate the area. Shrieks, skittering, rattling, scraping, crunching, and screaming can be heard within the sphere. Whenever a creature starts its turn in the sphere, it must make a DC 14 Wisdom saving throw, taking 4d8 psychic damage on a failed save, or half as much damage on a successful one. 

Hatred of the Living. If a healing spell is cast within 90 ft, the bone cleric can use Bone Shriek, if available, on the caster in a 90 ft cone. If the caster fails their save, their spell is interrupted and fails.