BriarHeart

All That Lives Must Die. The briarheart can cast Necromancy spells using its Wisdom spellcasting modifier. It is naturally a druid.

Spellcasting. The BriarHeart is an 18th-level spellcaster. Its spellcasting ability is Wisdom (spell save DC 17, +9 to hit with spell attacks). It has the following spells prepared:

Cantrips (at will): Toll the Dead, Shillelagh, Frostbite, Infestation

1st level (4 slots): Inflict Wounds, Absorb Elements, Faerie Fire, Cause Fear

2nd level (3 slots): Spike Growth, Ray of Enfeeblement, Hold Person

3rd level (3 slots): Call Lightning, Feign Death, Bestow Curse

4th level (3 slots): Blight, Giant Insect, Guardian of Nature, Grasping Vine

5th level (3 slots): Anti-Life Shell, Contagion (Flesh Rot), Geas ("gesh")

6th level (1 slot): Create Undead, Primitive Ward

7th level (1 slot): Regenerate

8th level (1 slot): Abi-dalzim's Horrid Wilting

9th level (1 slot): Storm of Vengeance

Turn Resistance. The BriarHeart has advantage on saving throws against any effect that turns undead.

Undead Fortitude. If damage reduces the BriarHeart to 0 hit points, it must make a Constitution saving throw with a DC of half the damage taken, unless the damage is radiant or from a critical hit. On a success, the BriarHeart drops to 1 hit point instead. If the BriarHeart's heart is ripped out, it loses this ability.

Bone Club. Melee Weapon Attack: +1 to hit, reach 5 ft., 1 target. Hit:  7 (2d6 + 1) bludgeoning damage. 

The Briarheart can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The lich regains spent legendary actions at the start of its turn.

Cantrip. The BriarHeart casts a cantrip.

Font of Horrors (Costs 2 Actions). The BriarHeart regenerates health, expending up to a total of 20 Hit Dice before a long rest.

Roar (Costs 2 Actions). The BriarHeart roars, and any creature within 10 feet of it must make a Dexterity saving throw. On a failed save, the creature is knocked back 15 feet and falls prone. On a successful save, the creature is only pushed 5 feet back.