Vogruk gains additional features while wearing the Mask of the Dragon Queen that are already accounted for in these statistics.

Special Equipment. Vogruk has the Mask of the Dragon Queen.

Vogruk wields a Blast Scepter(a very rare magic item that requires attunement). It can be used as an arcane focus. Whoever is attuned to the Blast Scepter gains resistance to fire and lightning damage and can, as an action, use it to cast thunderwave as a 4th-level spell (save DC 16) without expending a spell slot.

Vogruk wears a Ring of Spell Turning(a legendary magical item that requires attunement). While wearing this ring, Vogruk has advantage on saving throws against any spell that targets only him (not in an area of effect). In addition, if he rolls a 20 for the save and the spell is 7th level or lower, the spell has no effect on him and instead targets the caster, using the slot level, spell save DC, attack bonus, and spellcasting ability of the caster.

Legendary Resistance (4/Day). If Vogruk fails a saving throw, he can choose to succeed instead.

Draconic Majesty. While Vogruk is wearing no armor, he can add his Charisma bonus to his Armor Class.

Dragon Sight. Once per day, Vogruk can gain blindsight out to a range of 30 feet for 5 minutes.

Dragon Fire. If Vogruk deals fire damage to a creature or flammable object, it starts burning. At the start of each of its turns, a creature burning in this way takes 1d6 fire damage. A creature that can reach the burning target can use an action to extinguish the fire.

Water Breathing. Vogruk can breathe underwater.

Relentless Endurance. When Vogruk is reduced to 0 HP but not killed, he can drop to 1 HP instead once per long rest.

Savage Attacks. When Vogruk scores a critical hit, roll one of the dice an additional time and add it to the extra damage.

Actor. Vogruk has advantage on Deception and Performance checks when trying to pass himself off as a different person, and he can mimic the speech of another person or the sounds made by other creatures that he has heard (for at least 1 minute).

Elemental Affinity. When Vogruk casts a spell that deals damage of the type associated with fire, he can add +7 to one damage roll of that spell. At the same time, he can spend 1 sorcery point to gain resistance to that damage type for 1 hour.

Font of Magic. Vogruk has 20 sorcery points that he regains when he finishes a long rest. He can use his sorcery points to gain additional spell slots or sacrifice spell slots to gain additional sorcery points as a bonus action.

Magical Guidance. When Vogruk makes an ability check that fails, he can spend 1 sorcery point to reroll the d20 and he must use the new roll, potentially turning the failure into a success. 

Spellcasting. Vogruk is a 20th-level spellcaster. His spellcasting ability is Charisma (spell save DC 21, +13 to hit with spell attacks). Vogruk has following Sorcerer spells prepared:
Cantrips (at will): chill touch, control flames, eldritch blast, mage hand, message, minor illusion, prestidigitation
1st level (5 slots): detect magic, shield
2nd level (4 slots): mirror image, aganazzar's scorcher
3rd level (4 slots): counterspell, dispel magic, lightning bolt
4th level (4 slots): fire shield, greater invisibility
5th level (4 slots): telekinesis
6th level (3 slots): Disintegrate, globe of invulnerability, scatter
7th level (3 slots): crown of stars, teleport
8th level (2 slots): power word stun
9th level (2 slots): wish, gate

Draconic Presence. As an action, Vogruk can spend 5 sorcery points to create a 60-ft. aura of fear. For 1 minute or until he loses his concentration, each hostile creature that starts its turn there must succeed on a WIS saving throw (DC 21) or be charmed or frightened until the aura ends. 

Dragon Wings.  Vogruk can create (and dismiss) dragon wings as a bonus action to gain a flying speed equal to his current walking speed.

Chill Touch. Ranged Spell Attack: +13 to hit, range 240 ft., 1 target. Hit: 4d8) necrotic damage.

Eldritch Blast. Ranged Spell Attack: +13 to hit, range 240 ft., 1-4 targets. Hit: 1d10 x 4 beams) force damage.

If Vogruk is wearing the Mask of the Dragon Queen, he can take 4 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. Vogruk regains spent legendary actions at the start of his turn.

Cantrip. Vogruk casts a cantrip.

Fiery Teleport (Costs 2 Actions). Vogruk, along with any objects he is wearing or carrying, teleports up to 60 feet to an unoccupied space he can see. Each creature within 5 feet of Vogruk before he teleports takes 1d10 fire damage.

Hellish Chains (Costs 3 Actions). Vogruk targets one creature he can see within 30 feet of him. The target is wrapped in magical chains of fire and restrained. The restrained target takes 6d6 fire damage at the start of each of its turns. At the end of its turns, the target can make a DC 17 Strength saving throw, ending the effect on itself on a success.

Scorching Burst. (Costs 4 Actions). Vogruk chooses a point he can see within 60 feet of him. Each creature within 5 feet of that point must make a DC 17 Dexterity saving throw, taking 4d8 fire damage on a failed save, or half as much damage on a successful one.