Cordelia (Herald of Decay)

Legendary Resistance (3/Day). If the Herald fails a saving throw, it can choose to succeed instead.

Necrotic Healing. Any damage you would have taken from a necrotic attack, you are now healed for that value. 

Fungal Body. At 14th level, the fungal spores in your body alter you: you can’t be blinded, deafened, frightened, or poisoned, and any critical hit against you counts as a normal hit instead, unless you’re incapacitated.

Spellcasting. The Herald is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 20, +12 to hit with spell attacks). The lich has the following wizard spells prepared:

Cantrips (at will):  chill touch, dissolution, infestation, minor illusion, poison spray, primal savagery

1st level (4 slots): devil's due, inflict wounds, ice knife, ray of sickness, speak with animals

2nd level (3 slots): barkskin, blindness/deafness, flame blade, gentle repose, misty step, ray of enfeeblement[/spell], spider climb

3rd level (3 slots):  creeping rot, crimson harvest, gaseous form, spirit shroud

4th level (3 slots): blight, shadow of moil

5th level (2 slots): cloudkill, contagion, danse macabre, insect plague, negative energy flood

6th level (1 slot):  circle of death, harm

7th level (1 slot): finger of death

8th level (1 slot): earthquake, feeblemind

9th level (1 slot): invulnerability

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

Paralyzing Touch. Melee Spell Attack: +12 to hit, reach 5 ft., one creature. Hit: 10 (3d6) cold damage. The target must succeed on a DC 24 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Symbiotic Entity. You can use Wild Shape to awaken the spores that infuse you to gain 72 temp HP, roll double damage dice for your Halo of Spores damage, and deal 1d6 additional necrotic damage when you hit with a melee weapon attack. These all last for 10 minutes, or until you lose all these temporary hit points, or until you use your Wild Shape again.

Spreading Spores. As a bonus action while your Symbiotic Entity feature is active, you can hurl spores up to 30 feet away, where they swirl in a 10-foot cube for 1 minute. The spores disappear early if you use this feature again, if you dismiss them as a bonus action, or if your Symbiotic Entity feature is no longer active.
Whenever a creature moves into the cube or starts its turn there, that creature takes your Halo of Spores damage, unless the creature succeeds on a Constitution saving throw (DC 24). A creature can take this damage no more than once per turn.

Halo of Spores. You can use your reaction to deal 1d10 necrotic damage to one creature you can see when it moves into a space within 10 feet of you or starts its turn there, if it fails a CON saving throw (DC 24).

Fungal Infestation. If a beast or a humanoid that is Small or Medium dies within 10 feet of you, you can use your reaction to animate it, as a zombie under your control, with 1 hit point. In combat, the zombie’s turn comes immediately after yours. It obeys your mental commands, and the only action it can take is the Attack action, making one melee attack.

Circle of Decay. As a reaction to being hit, the Herald creates a 15 ft. radius of spores. Anybody in the radius takes 2d12 damage on a failed CON saving throw (DC 16), and half as much on a successful one. Any damage taken heals the Herald for the same amount.

The Herald 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 Herald regains spent legendary actions at the start of its turn.

Cantrip. The Herald casts a cantrip.

Paralyzing Touch (Costs 2 Actions). The Herald uses its Paralyzing Touch.

Frightening Gaze (Costs 2 Actions). The Herald fixes its gaze on one creature it can see within 10 feet of it. The target must succeed on a DC 24 Wisdom saving throw against this magic or become frightened for 1 minute. The frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a target’s saving throw is successful or the effect ends for it, the target is immune to the lich’s gaze for the next 24 hours.

Disrupt Life (Costs 3 Actions). Each non-undead creature within 20 feet of the lich must make a DC 24 Constitution saving throw against this magic, taking 21 (6d6) necrotic damage on a failed save, or half as much damage on a successful one.