Crystal, Possessed

Reckless Attack. When Crystal makes his first attack on his turn, he can decide to attack recklessly, giving himself advantage on melee weapon attack rolls using Strength during this turn, but attack rolls against him have advantage until his next turn.

Rage. Twice per day, as a bonus action, Crystal can enter a rage that lasts for one minute. While raging, he gains advantage on Strength checks and saving throws, as well as a +4 bonus to melee damage rolls. He also gains resistance to bludgeoning, piercing, and slashing damage.

Arcane Blade. Crystal's longsword functions as an arcane focus, allowing him to channel magical energy through it. He gains a +3 bonus to attack and damage rolls made with the sword. Additionally, he can use his bonus action to imbue the sword with additional magic, causing it to deal an additional 4d6 force damage on a hit. This effect lasts for one minute or until Crystal uses his bonus action to end it.

Possessed by Sharruth. Crystal is currently possessed by an elder-god fire dragon named Sharruth. This grants him resistance to fire damage and immunity to being frightened. Sharruth can communicate telepathically with Crystal and can control his actions if he chooses to do so.

Dragon Ward. Sharruth has granted Crystal the power to ward himself against dragon attacks. He gains resistance to fire damage and has advantage on saving throws against the breath weapons of dragons.

Spellcasting. Crystal is a 20th-level Warlock. His spellcasting ability is his Charisma. Crystal has following spells prepared:

Cantrips (at will): eldritch blast, mage hand, prestidigitation

1st-level (4 slots): armor of Agathys, hex, hellish rebuke, unseen servant

2nd-level (3 slots): hold person, invisibility, mirror image

3rd-level (3 slots): counterspell, fly, hunger of Hadar

4th-level (3 slots): banishment, blight, dimension door

5th-level (2 slots): dominate person, hold monster

6th-level (1 slot): circle of death

Multi-Attack. Crystal makes three actions per turn: Three attacks with his longsword, or two attacks with his longsword and one with his breath weapon.

Longsword. Melee Weapon Attack: +23 to hit, reach 5 ft., one target. Hit: 15 (2d8+10) slashing damage plus 7 (2d6) fire damage.

Breath Weapon (Recharge 5-6). Crystal can use an action to exhale destructive energy in a 60-foot cone. Each creature in that area must make a DC 24 Dexterity saving throw, taking 63 (18d6) fire damage on a failed save, or half as much damage on a successful one.

Legendary Actions (3/round).
Crystal 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. Crystal regains spent legendary actions at the start of his turn.

Move. Crystal moves up to his speed without provoking opportunity attacks.

Longsword Attack. Crystal makes one extra longsword attack.

Breath Weapon (Costs 2 actions). Crystal uses his breath weapon.

True Suffering (Costs 3 Actions). Crystal and Sharruth unleash a wave of pure agony, suffering, and fire, causing all creatures within a 60-foot radius to make a Wisdom saving throw (DC 25). On a failed save, creatures takes 10d10 fire damage and are stunned for one minute. On a successful save, creatures take half damage and are not stunned. Additionally, creatures that fail the save have disadvantage on all attacks and ability checks for one minute due to the overwhelming pain. This ability can only be used once per long rest.