Adult Black Dragon

The adult black dragon can breathe air and water.

3/day (4/day in lair). If the adult black dragon fails a saving throw, it can choose to succeed instead.

The adult black dragon makes three Rend attacks. It can replace one attack with a use of Spellcasting to cast Melf's Acid Arrow (level 3 version).

Melee Weapon Attack: +11 to hit, reach 10 ft.. Hit: 13 (2d6 + 6) slashing plus 4 (1d8) acid damage.

Recharge 5–6. Dexterity Saving Throw: DC 18, each creature in a 60-foot-long, 5-foot-wide Line.
Failure: 54 (12d8) acid damage.
Success: Half damage.

1 use per day. The adult black dragon casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 17, +9 to hit with spell attacks):
At Will: Detect Magic, Fear, Melf's Acid Arrow (level 3 version)
1/Day Each: Speak with Dead, Vitriolic Sphere

Dexterity Saving Throw: DC 17, one creature the adult black dragon can see within 120 feet.
Failure: 22 (4d10) poison damage, and the target has Disadvantage on saving throws to maintain Concentration} until the end of its next turn.
Failure or Success: The adult black dragon can't take this action again until the start of its next turn.

The adult black dragon casts Fear, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 17). The adult black dragon can't take this action again until the start of its next turn.

The adult black dragon moves up to half its Speed, and it makes one Rend attack.