Bartholomew the Barrel Beast

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

Spellcasting. Bartholomew the Barrel Beast is a 16-level spellcaster. Its spellcasting ability is Wisdom (spell save DC 22, +5 to hit with spell attacks). Bartholomew the Barrel Beast has the following spells prepared at all times:
Cantrips (at will): Eldritch blast, Acid Splash, Chill Touch, Poison Spray, Resistance
1st level (5 slots): Chromatic Orb, Detect magic, Feather Fall, Fog Cloud, Guiding Bolt
2nd level (4 slots):Shatter
3rd level (3 slots):Counterspell, Fear
4th level (2 slots): Blight
5th level (2 slots): Animate Objects, Contagion
6th level (2 slots):Eyebite
7th level (2 slots):Finger of death, Regenerate
8th level (2 slots): Antimagic Field, Mind Blank(Automatically used on self)
9th level (1 slots, automatically used to get the jump on players):True Polymorph

Multiattack. Bartholomew makes three attacks: one with its tail and two with its arms.

Metalic smash. Melee Weapon Attack: +10 to hit, reach 20 ft., one target. Hit: 26 (4d12 + 2) Bludgeoning damage. 

Tail of Tall Tales. Melee Weapon Attack: +15 to hit, reach 10ft., Aoe, Hit: 20(1d20+10) Emotional Damage.

Barrel Blast. Ranged Weapon Attack: +8 to hit, range #5/50 ft., one target. Hit: 22 (4d8 + 6) force damage.

Potion of Greater Healing (Recharge 6): Bartholomew drinks one potion of greater healing.

Potion of Necrotic Resistance (once per long rest): Bartholomew drinks one potion of necrotic Resistance.

Potion of Fire Resistance (once per long rest): Bartholomew drinks one potion of Fire Resistance.

Bartholomew the Barrel Beast can take two legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of a creature's or player's turn. Bartholomew regains spent legendary actions after six of it's turns.

Dispense potion (Costs 0 Actions). One potion of the DM's choice comes out of Bartholomew's body
Scatter potion (Costs 1 Action) The dispensed potion is spread over a 10-foot radius of any point within 20 feet of Bartholomew, there has to be a dispensed potion, or this action cannot be taken, upon using this action the dispensed potion counts as used

Consume potion (Costs 1 Action). The effects of the dispensed potion are given to Bartholomew the Barrel Beast. These effects last until Bartholomew's next long rest. There has to be a dispensed potion, or this action cannot be taken, upon using this action the dispensed potion counts as used