Black Dragon Master, Veteran

Dragon Student. The Veterans's bond with its dragon partner (and patron) gives it access to an expanded spell list and a adult black dragon companion. The dragon partner can cast spells as an action in place of the Veteran (using the Veteran's spellcasting modifiers), use its Breath Weapon action in place of the Veteran's action, or take the Multiattack action from its stat block using the Veteran's bonus action. Three times per day, when the dragon partner makes a Bite attack, it can deal additional damage of its type or recover health points (its choice) equal to 1d6+15. It takes the dodge action if not given any commands, but if the Veteran is incapacitated, it will take any action it deems necessary. The Veteran gains a swimming speed of 30 ft and can breath water.

Dragon Pact. The Veteran and its dragon partner share spell slots (which are recovered after a short rest), but all spells cast by your dragon partner become damage of its respective type. Whenever the dragon partner casts or uses a spell, it can add the Veteran's Charisma bonus to one damage roll for that spell. It can also cast eldritch blast as a modified breath weapon (see actions). The Veteran concentrates on any spell cast by it or the dragon partner that require concentration, and has advantage on concentration checks. Whenever the dragon partner casts or uses as a spell, it gains 6 temporary hit points. 

Dragon Warrior. The Veteran can use its Charisma instead of Dexterity or Strength for its attack and damage rolls when using one-handed weapons. These weapons are considered a spellcasting focus. When it hits with an attack, it deals an additional acid damage with that weapon equal to its Charisma bonus.If the Veteran is riding its dragon partner, it can make a weapon attack as a bonus action if the dragon partner takes an action to cast a spell or use its breath weapon. The dragon partner can now use the modified eldritch blast as a bonus action, instead of an action. When making an opportunity attack, it can cast a spell that targets only that creature instead of using a weapon. It can also add its Charisma bonus to any Intelligence ability check it makes.

Innate Spellcasting. The dragon partner’s innate spellcasting ability is Charisma (spell save DC 18). It can innately cast the following spells:

3/day each- melf's acid arrow, vitriolic sphere

1/day- insect plague

Spellcasting. The Veteran is a 15th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). The Veteran has following warlock spells prepared:

(at will): booming blade, eldritch blast, mage hand, prestidigitation, armor of agathys, jump, alter self

at 5th level (4 slots): absorb elements, hex, shield, dragon's breath, flaming sphere, invisibility, counterspell, fireball, lightning bolt, dimension door, freedom of movement, wall of fire, bigby's hand, cone of cold, synaptic static

1/day each- true seeing, forcecage, feeblemind

Acid Blast (Eldritch Blast). The dragon partner exhales acid in a 60-­foot line that is 10 feet wide.. Each creature in that area must make a DC 18 Dexterity saving throw, taking 27 (4d10+5) acid damage on a failed save, or half as much damage on a successful one.

Longsword. Melee Weapon Attack: +10 to hit, reach 5 ft., 1 target. Hit: 10 (1d8+5) slashing damage + 5 acid damage.

Acid Breath (Recharge 5–6). The dragon partner exhales acid in a 60-­foot line that is 5 feet wide. Each creature in that line must make a DC 18 Dexterity saving throw, taking 54 (12d8) acid damage on a failed save, or half as much damage on a successful one.

War Caster. The veteran can cast a spell that targets only 1 creature and has a cast time of 1 action or bonus action as an opportunity attack.