Ancient Black Dragon

Gargantuan / dragon / Chaotic Evil / CR 21

Armor Class22
Hit Points367 (21d20 + 147)
Speed40 ft, fly 80 ft, swim 40 ft
Challenge21
Proficiency-
STR27+8
DEX14+2
CON25+7
INT16+3
WIS15+2
CHA22+6
Senses

Blindsight 60 ft, Darkvision 120 ft

Languages

Common, Draconic

Damage immunities

Acid

Traits

Amphibious

The monster can breathe air and water.

Legendary Resistance

Special

If the monster fails a saving throw, it can choose to succeed instead.

Actions

Multiattack

Action

The monster makes three attacks. It can replace one attack with a use of to cast Melf's Acid Arrow (level 4 version).

Rend

Action

. .

Acid Breath

Action

Dexterity Saving Throw: DC , each in a -foot-long, -foot-wide Line.
Failure: damage.
Success: Half damage.

Spellcasting

Action

The monster casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC , +13 to hit with spell attacks):
At Will: Detect Magic, Fear, Melf's Acid Arrow (level 4 version)
1/Day Each: Create Undead, Speak with Dead, Vitriolic Sphere (level 5 version)

Prepared Spells

Detect Magic, Fear, Melf'S Acid Arrow, Create Undead, Speak With Dead, Vitriolic Sphere, Fear

Referenced spells