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

Magic Resistance.  Achnalogia has advantage on saving throws against spells and other magical effects.

Anti-Magic Aura. Achnalogia has a 200 foot radius around it, preventing any spells from being casted in this area. If any spell is being concentrated on and enters the area, the concentration will end.

Multiattack. Achnalogia can use its Frightful Presence. It then makes five attacks: one with its bite, two with its claws, one with its horns, and one with its tail. It can use its Swallow instead of its bite.

Bite. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 56 (4d12 + 10) piercing damage. If the target is a creature, it is grappled (escape DC 20). Until this grapple ends, the target is restrained, and Achnalogia can’t bite another target.

Claw. Melee Weapon Attack: +19 to hit, reach 15ft., one target. Hit: 68 (4d8 + 10) slashing damage.

Horns. Melee Weapon Attack: +19 to hit, reach 10ft., one target. Hit: 42 (4d10 + 10) piercing damage.

Tail. Melee Weapon Attack: +19 to hit, reach 20ft., one target. Hit: 44 (4d6 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 20 Strength saving throw or be knocked prone.

Frightful Presence. Each creature of Achnalogia choice within 200 feet of it and aware of it must succeed on a DC 20 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if Achnalogia is within line of sight, 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 Achnalogia’s Frightful Presence for the next 24 hours.

Swallow. Achnalogia makes one bite attack against a Large or smaller creature it is grappling. If the attack hits, the target takes the bite’s damage, the target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside Achnalogia, and it takes 56 (16d6) acid damage at the start of each of Achnalogia’s turns.

If Achnalogia takes 60 damage or more on a single turn from a creature inside it, Achnalogia must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of Achnalogia. If Achnalogia dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

Dragon Breath (Recharge 5–6). The dragon exhales ፪ዪቹልፕⶴ in a 160-­foot line that is 20 feet wide. Each creature in that line must make a DC 28 Constitution saving throw, taking 54 (12d8) damage on a failed save, or half as much damage on a successful one.

Achnalogia 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. Achnalogia regains spent legendary actions at the start of its turn.

Attack. Achnalogia makes one claw attack or tail attack.

Move. Achnalogia moves up to half its speed.

Chomp (Costs 2 Actions). Achnalogia makes one bite attack or uses its Swallow.