Ancient Gray Dragon

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

Mimicry. The dragon can mimic any sounds it has heard, including voices. A creature that hears the sounds can tell they are imitations with a successful DC 19 Wisdom (Insight) check.

Rage (3/Day). As a bonus action, the dragon can enter a rage. While raging, it gains the following benefits:

• The dragon has advantage on Strength checks and Strength saving throws.

• When the dragon makes a melee weapon attack, it gains a +4 bonus to the damage roll.

• The dragon has advantage on saving throws against spells and other magical effects.

Its rage lasts for 1 minute. It only ends early if the dragon is knocked unconscious or if it chooses to end its rage on its turn as a bonus action.

Ravenous Onslaught. When the dragon reduces a creature to 0 hit points or scores a critical hit with a melee attack on its turn, it can take a bonus action to fly up to half its flying speed and make a bite attack (it must start and end this movement on the ground).

Vicious Critical. The dragon's melee weapon attacks score a critical hit on a roll of a 19 or 20. In addition, it rolls one additional weapon damage die when determining the extra damage for a critical hit with a melee weapon attack.

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +16 to hit, reach 15 ft., one target. Hit: 22 (2d12 + 9) piercing damage plus 14 (4d6) necrotic damage. The target’s hit point maximum is reduced by an amount equal to the necrotic damage taken, and the fang dragon regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if its hit point maximum is reduced to 0.

Claw. Melee Weapon Attack: +16 to hit, reach 10 ft., one target. Hit: 18 (2d8 + 9) slashing damage.

Tail. Melee Weapon Attack: +16 to hit, reach 20 ft., one target. Hit: 20 (2d10 + 9) bludgeoning, piercing or slashing damage. If the target is a creature, it must succeed on a DC 24 Strength saving throw or be knocked prone.

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.

Predatory Roar (Recharge 5–6). The dragon exhales a thundering roar in a 90-foot cone. Each creature in that area must make a DC 24 Dexterity saving throw, taking 56 (16d6) force damage, knocked prone, and applied the deafened condition on a failed save, or half as much damage on a successful one.

The dragon 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. The dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Tail Sweep (Costs 2 Actions). The dragon spins and thrashes out with its tail. Each creature within 20 feet of the dragon must succeed on a DC 24 Dexterity saving throw or take 20 (2d10 + 9) bludgeoning or slashing damage and be knocked prone.