Warlock Supreme of the Great Old One

Superior Pact. The Warlock Supreme has formed a pact with a powerful creature and with it has received many gifts, one of which is the spellcasting ability. This Warlock has chosen to renew this pact and pay extra for additional gifts. The price for this pact can be decided by the DM, such as the loss of a limb, infertility, the ownership of its soul, exe. In addition to all the abilities mentioned below, whenever it casts a spell that would damage a target, the Warlock supreme can choose to change the damage type to psychic.

Psychic Barrier. The Warlock Supreme's devotion to its Patron has given it a psychic barrier that gives it resistance to Psychic damage as well as gives the Warlock Supreme a base AC of 18. It can also speak telepathically up to 60 feet and can not have its thought read unless it is willing.

Devil's Sight.  Magical Darkness does not affect the Warlock Supreme's Darkvision.

Create Thrall. The Warlock Supreme can infect the mind of another creature using the power of its Patron. It can use its action to charm an incapacitated humanoid. This humanoid remains charmed until the remove curse spell is cast on it, the charm is removed or when the Warlock Supreme uses this ability again.

The warlock Supreme can communicate telepathically with the charmed creature as long as the two are on the same plane of existence.

Agonizing Blast. When the Warlock Supreme casts eldritch blast, it adds its Charisma modifier to the damage it deals on a hit.

Mystic Arcanum: The Warlock Supreme can cast the following spells in addition the those mentioned in the Spellcasting feature and can cast them once per long rest without expending a spell slot:
2nd level: Detect thoughts
6th level: Arcane Gate, true seeing
7th level: Forcecage

Spellcasting. The Warlock Supreme is a 14-level spellcaster. Its spellcasting ability is Charisma (spell save DC 19, 11 to hit with spell attacks). It requires no material components to cast its spells. The Warlock Supreme has following Warlock spells prepared:
Cantrips (at will): eldritch blast, guidance, mage hand, mind sliver, prestidigitation, toll the dead.
5th level (3 slots): armor of Agathys, arms of Hadar, detect magic, hex, enthrall, crown of madness, mind spike,  bestow curse, charm monster, hold monster, synaptic static.

Multiattack. The Warlock Supreme makes two dagger attacks.

Dagger. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 10 (2d4 + 4) [Slashing] damage, plus 22 (4d10) psychic damage.

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

Pact Favor (Costs 1 Action). The Warlock supreme can reduce their hit point maximum by 15 to restore a single spell slot. Their hit point maximum restores after a long rest.

Eldritch bomb (Costs 1 Action). All creature within 10 feet of the warlock must make a DC19 Charisma saving throw or take 15 (3d10) Psychic damage and be pushed back 10 feet on a failed save. On a successful save the creature takes no damage and isn't pushed back.