Cambium Queen

Magic Resistance. The cambium queen has advantage on saving throws against spells or spell like effects.

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

Innate Spellcasting. The cambium queen's spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). The cambium queen can innately cast the following spells, requiring no components: 
At Will: alter self, detect magic, detect thoughts, healing word, hold person, plane shift 
4 slots: burning hands, ray of sickness (4d8), invisibility, animate dead
3 slots: haste, lightning bolt, toll the dead, inflict wounds 
1 slot: finger of death, vampiric touch (7th level)

Spider Climb. The cambium queen can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Immortal Mind (Mythic Trait; Recharges after a Short or Long Rest). If the cambium queen is reduced to 0 hit points, as long as there are other cambiums that are still alive another cambium within the lair is suddenly and violently transformed into the cambium queen. They have 200 hit points and 100 temporary hit points from the influx of humors, and anyone who sees the transformation must make a Wisdom saving throw (DC 20) against fear. Creatures who are afraid of the cambium queen have disadvantage on all attacks and saving throws.

Telepathic Hub. The cambium queen can use telepathy to initiate and maintain telepathic conversations with any other cambiums within 5 miles of it. The cambium queen can also allow these creatures to communicate telepathically with each other. 

Multiattack. The cambium queen makes 4 needle finger attacks, or 1 bite and casts a spell.

Bite. Melee Weapon Attack: +13 to hit, reach 5 ft., 1 target. Hit: 17 (2d8 +7) piercing damage. Additionally, when a creature is hit by the bite attack, they must make a DC 21 Constitution saving throw or suffer the effects of the Embalming Flux.

Needle Fingers. Melee Weapon Attack: +13 to hit, reach 10 ft., 1 target. Hit: 25 (3d10 + 7) piercing damage. In addition, the target must succeed a DC 21 Constitution saving throw; if it fails, the cambium queen can inflict Ability Damage, Imbalance Humors, or Siphon Spell Slots on the target. A target only makes a saving throw once per turn, even if it is struck by multiple needle finger attacks.
Ability Damage (4/Day). When the target of the cambium queen's needle fingers fails its saving throw, its Strength, Dexterity, or Constitution ability score (cambium queen's choice) is reduced by 1d4 until it finishes a long rest. If this reduces a score to 0, the target is incapacitated until it gains at least 1 point. If a creature has two of these ability scores reduced to 0, they die.
Imbalance Humors (Recharge 4-6). When the target of the cambium queen's needle fingers fails its saving throw, apply one of the following effects:
Sanguine Flux: The target cannot be healed - naturally or magically - until their next long rest.
Choleric Flux: The target becomes confused (as the spell) for 3d6 rounds. The target can repeat this saving throw at the end of each of its turns to shrug off the flux before the duration ends.
Melancholic Flux: The target is incapacitated for 1d4 rounds and slowed (as the spell) for 3d6 rounds after. The target can repeat this saving throw at the end of each of its turns to shrug off the flux before the duration ends.
Phlegmatic Flux: The target gains 1 level of exhaustion which lasts for 3d6 rounds. The target can repeat this saving throw at the end of each of its turns to shrug off the flux before the duration ends.
Embalming Flux: The target become rigid and staggered for 3d6 rounds. While staggered, a creature can only take 1 standard action or a move action, and cannot take bonus actions or reactions. The target can repeat this saving throw at the end of each of its turns to shrug off the flux before the duration ends. However, if they fail three saving throws in a row, the target becomes paralyzed for the remainder of the duration.
Siphon Spell Slots: When the cambium queen is out of uses for her innate spellcasting, she can siphon the ability from other spell casters and non-casters. When a creature fails a saving throw against her needle fingers, she deals 1d4 damage to their Intelligence, Wisdom, or Charisma scores. For every 2 points of ability damage, the cambium queen regains 1 "spell slot".

Hemorrhage. When a creature the cambium queen is targeted by a spell or spell like ability, and she has already attacked that creature with her needle fingers, she can force the caster to make a Constitution saving throw DC21. On a failure, the spell fails and the caster takes 2d10 necrotic damage. On a success, the spell functions as normal.
The cambium queen must successfully hit the caster again with her needle fingers to use this reaction again.

The cambium queen can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time, and only at the end of another creatures turn. The cambium queen regains spent legendary actions at the start of its turn.

Needle Fingers. The cambium queen makes an attack with her needle fingers.
Casting. The cambium queen casts a spell.
Hemorrhage (Costs 2 Actions). The cambium queen forces a creature who she has successfully hit with her needle finger attack. The creature makes a DC 21 Constitution saving throw; on a failure, they take 2d10 necrotic damage. On a success, they take half as much damage.

If the cambium queen's mythic trait immortal mind is active, she can use the options below as legendary actions for 1 hour after activating it.

Numbing Claws. The cambium queen makes 2 needle fingers attacks. If both are against the same creature, it takes an extra 2d6 poison damage and must make a DC 21 Constitution saving throw or become paralyzed until the end of their next turn.
Imbalance Humors. The cambium queen recharges imbalance humors, makes 2 needle finger attacks on one target and uses it.