Ancient Black Dragon

The monster can breathe air and water.

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

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

Melee Attack: +15 to hit. reach 5 ft. Hit: 2d8 + 8 slashing plus 2d8 acid damage.

Dexterity Save: DC 22. target: 90-foot-long, 10-foot-wide line, creature. Failure: 15d8 acid damage; success: half.

The monster casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (+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)

For the duration, you sense the presence of magical effects within 30 feet of yourself. If you sense such effects, you can take the Magic action to see a faint aura around any visible creature or object in the area that bears the magic, and if an effect was created by a spell, you learn the spell's school of magic. The spell is blocked by 1 foot of stone, dirt, or wood; 1 inch of metal; or a thin sheet of lead.

Each creature in a 30-foot Cone must succeed on a Wisdom saving throw or drop whatever it is holding and have the Frightened condition for the duration. A Frightened creature takes the Dash action and moves away from you by the safest route on each of its turns unless there is nowhere to move. If the creature ends its turn in a space where it doesn't have line of sight to you, the creature makes a Wisdom saving throw. On a successful save, the spell ends on that creature.

A shimmering green arrow streaks toward a target within range and bursts in a spray of acid. Make a ranged spell attack against the target. On a hit, the target takes 4d4 Acid damage and 2d4 Acid damage at the end of its next turn. On a miss, the arrow splashes the target with acid for half as much of the initial damage only. Using a Higher-Level Spell Slot. The damage (both initial and later) increases by 1d4 for each spell slot level above 2.

You can cast this spell only at night. Choose up to three corpses of Medium or Small Humanoids within range. Each one becomes a Ghoul under your control (see the Monster Manual for its stat block). As a Bonus Action on each of your turns, you can mentally command any creature you animated with this spell if the creature is within 120 feet of you (if you control multiple creatures, you can command any of them at the same time, issuing the same command to them). You decide what action the creature will take and where it will move on its next turn, or you can issue a general command, such as to guard a particular place. If you issue no commands, the creature takes the Dodge action and moves only to avoid harm. Once given an order, the creature continues to follow the order until its task is complete. The creature is under your control for 24 hours, after which it stops obeying any command you've given it. To maintain control of the creature for another 24 hours, you must cast this spell on the creature before the current 24-hour period ends. This use of the spell reasserts your control over up to three creatures you have animated with this spell rather than animating new ones. Using a Higher-Level Spell Slot. If you use a level 7 spell slot, you can animate or reassert control over four Ghouls. If you use a level 8 spell slot, you can animate or reassert control over five Ghouls or two Ghasts or Wights. If you use a level 9 spell slot, you can animate or reassert control over six Ghouls, three Ghasts or Wights, or two Mummies. See the Monster Manual for these stat blocks.

You grant the semblance of life to a corpse of your choice within range, allowing it to answer questions you pose. The corpse must have a mouth, and this spell fails if the deceased creature was Undead when it died. The spell also fails if the corpse was the target of this spell within the past 10 days. Until the spell ends, you can ask the corpse up to five questions. The corpse knows only what it knew in life, including the languages it knew. Answers are usually brief, cryptic, or repetitive, and the corpse is under no compulsion to offer a truthful answer if you are antagonistic toward it or it recognizes you as an enemy. This spell doesn't return the creature's soul to its body, only its animating spirit. Thus, the corpse can't learn new information, doesn't comprehend anything that has happened since it died, and can't speculate about future events.

You point at a location within range, and a glowing, 1-foot-diameter ball of acid streaks there and explodes in a 20-foot-radius Sphere. Each creature in that area makes a Dexterity saving throw. On a failed save, a creature takes 10d4 Acid damage and another damage at the end of its next turn. On a successful save, a creature takes half the initial damage only. Using a Higher-Level Spell Slot. The initial damage increases by 2d4 for each spell slot level above 4.

Dexterity Save: DC 21. target: creature. Failure: 6d10 poison damage.

The monster casts Fear. The monster can't take this action again until the start of its next turn.

Each creature in a 30-foot Cone must succeed on a Wisdom saving throw or drop whatever it is holding and have the Frightened condition for the duration. A Frightened creature takes the Dash action and moves away from you by the safest route on each of its turns unless there is nowhere to move. If the creature ends its turn in a space where it doesn't have line of sight to you, the creature makes a Wisdom saving throw. On a successful save, the spell ends on that creature.

The monster moves up to half its Speed, and it makes one Rend attack.