Argonax the Black

Amphibious. Argonax can breathe air and water.

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

Shapeshifter. Argonax learned from a dragon whose name has been forgotten to the flow time, the ability to change his shape. As an action, Argonax is able to take on the shape of any humanoid race that he so wishes or back into his true form. Argonax reverts to his true form if he dies. Any equipment he is wearing or carrying is absorbed or borne by the new form (the Argonax's choice).

In a new form, Argonax retains his alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, spellcasting abilities, and Intelligence, Wisdom, and Charisma scores, as well as this action. His statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.

Spellcasting. Throughout the centuries that he has been alive, Argonax has captured many a wizard and tortured the secrets of magic out of them. In this way he has become a 16th level spellcaster. His spellcasting ability is Intelligence (spell save DC 17, +7 to hit with spell attacks). Argonax has the following wizard spells prepared:

Cantrips (at will): lightning lure, mage hand, toll the dead, prestidigitation

1st level (4 slots): charm person, magic missile, alarm, grease, sleep

2nd level (3 slots): arcane lock, crown of madness, misty step, hold person

3rd level (3 slots): counterspell, haste, lightning bolt, slow

4th level (3 slots): secret chest, polymorph, dimension door, blight

5th level (3 slots): geas, animate objects, conjure elemental, telekinesis

6th level (2 slots): circle of death, disintegrate, guards and wards, magic jar

7th level: (1 slot): symbol, plane shift, finger of death

8th level (1 slot): power word stun, feeblemind

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws; alternatively, it can cast 1 spell of any level that it knows and 1 cantrip.

Bite. Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 19 (2d10 + 8) piercing damage plus 9 (2d8) acid damage.

Claw. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 15 (2d6 + 8) slashing damage.

Tail. Melee Weapon Attack: +15 to hit, reach 20 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Acid Breath (Recharge 5–6). The dragon exhales acid in a 90-foot line that is 10 feet wide. Each creature in that line must make a DC 22 Dexterity saving throw, taking 67 (15d8) acid damage on a failed save, or half as much damage on a successful one.

Argonax 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. He regains spent legendary actions at the start of his turn.

Cast a Spell. Argonax casts spell of 5th level or lower.

Detect. Argonax makes a Wisdom (Perception) check.

Tail Attack. Argonax makes a tail attack.

Wing Attack (Costs 2 Actions). Argonax beats his wings. Each creature within 15 feet of the dragon must succeed on a DC 23 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. Argonax can then fly up to half his flying speed.