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CR 21 dragon • D&D 5e Homebrew Creature
Created by @LightReign
Gargantuan dragon, Chaotic Evil
The apex of draconic corruption. Ancient, cunning, and utterly without mercy — this CR 21 colossus commands swamps, undead, and acid with the patience of centuries.
If the Ancient Black Dragon fails a saving throw, it can choose to succeed instead (4/Day, or 5/Day in Lair).
The Ancient Black Dragon can breathe air and water.
The Ancient Black Dragon makes three Rend attacks. It can replace one attack with a use of Spellcasting to cast Acid Arrow (level 4 version).
Melee Attack Roll: +15, reach 15 ft.
Hit: 17 (2d8 + 8) Slashing damage plus 9 (2d8) Acid damage.
Dexterity Saving Throw: DC 22, each creature in a 90-foot-long, 10-foot-wide Line.
Failure: 67 (15d8) Acid damage.
Success: Half damage.
The Ancient Black Dragon casts one of the following spells, requiring no material components and using Charisma as the spellcasting ability (spell save DC 21, +13 to hit with spell attacks):
At will: Acid Arrow (level 4 version), Detect Magic, Fear
1/Day each: Create Undead, Speak with Dead, Vitriolic Sphere (level 5 version)
Dexterity Saving Throw: DC 21, one creature the Ancient Black Dragon can see within 120 feet.
Failure: 33 (6d10) Poison damage, and the target has Disadvantage on saving throws to maintain Concentration until the end of its next turn.
Failure or Success: The Ancient Black Dragon can't take this action again until the start of its next turn.
The Ancient Black Dragon uses Spellcasting to cast Fear. The dragon can’t take this action again until the start of its next turn
The Ancient Black Dragon moves up to half its Speed, and it makes one Rend attack.
Official D&D 5th Edition creature from the System Reference Document 5.2. Stats, abilities, and descriptions are faithful to the original SRD text.
This is one of the most dangerous creatures in the SRD and demands respect at the table. A few things to keep in mind:
The Ancient Black Dragon is patient and paranoid in equal measure. It doesn't open with Acid Breath — it observes, uses Fear via Legendary Actions to fragment the party, then picks off isolated targets with Rend multiattacks before committing to a breath weapon.
Acid Arrow at will is easy to forget but punishing. The dragon can cast it as part of its Multiattack, meaning it's almost always doing three things per turn. Legendary Resistance jumps to 5/Day in its lair — if you're running a lair encounter, the party's save-or-suck spells are largely wasted. Make sure your players feel that difference.
Cloud of Insects as a Legendary Action is underrated. Disadvantage on Concentration saves shuts down the party's most powerful sustained spells mid-fight. Prioritise casters.
Amphibious means it will drag the fight into water if given the chance. Design the encounter space with this in mind — a lair with flooded chambers heavily favours the dragon.
Create Undead and Speak with Dead hint at a creature that has been collecting secrets and servants for centuries. Consider seeding the lair with undead thralls before the dragon itself appears.
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