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

Keen Hearing: The Viteus Aberra has advantage on Wisdom (Perception) checks that rely on hearing

Bad Eyesight: The Viteus Aberra has disadvantage on Wisdom (Perception) checks that rely on sight

Flammable. When Viteus Aberra is dealt fire damage it makes a DC 20 Constitution saving throw, if it succeeds, it takes no damage and its next attack does an extra 14 (3d8) fire damage

Compulsion. When any devotee of The Order of Crimson Snowfall comes within a mile of Viteus Aberra they are drawn to it and they want to fulfill its desires

Multiattack. Viteus Aberra can use its Frightful Presence. It then makes three attacks: one with its tail and two with its claws.

Shred Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 17 (2d10 + 6) piercing damage plus 4 (1d8) acid damage.  

Claw. Melee Weapon Attack: +11 to hit, reach 15ft., one target. Hit: 13 (2d6 + 6) slashing damage.

Tail. Melee Weapon Attack: +11 to hit, reach 50 ft., one target. Hit: 19 (2d10+ 8) bludgeoning damage. On a hit Target must make a DC 18 Dexterity (acrobatics) check or be grappled, The grappled creature can make a new saving throw at the beginning of the turn, Viteus Aberra can only have two creatures grappled this way.

Frightful Presence. Each creature of the Beast's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 16 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.

Swallow. The tarrasque 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 the tarrasque, and it takes 14 (4d6) acid damage at the start of each of Viteus Aberra’s turns.

If the Viteus Aberra takes 40 damage or more on a single turn, the Viteus Aberra must succeed on a DC 15 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the tarrasque. If Viteus Aberra dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

Tail Whip (Recharge 5–6). Viteus Aberra whips its tail at one target, it makes a Dexterity saving throw taking 33 (6d10) Piercing damage on a failed save, or half as much damage on a successful one, and is knocked prone.

Viteus Aberra 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 Beast regains spent legendary actions at the start of its turn.

Detect. Viteus Aberra makes a Wisdom (Perception) check.

Tail Attack. Viteus Aberra makes a tail attack.

Move. Viteus Aberra moves up to half its speed.