Updog

Legendary Vulnerability (3/Day). If the updog succeeds a saving throw, it can choose to fail instead.

Magic Vulnerability. The updog has disadvantage on saving throws against spells and other magical effects.

Absorbant dog. Any time the updog is targeted by a magic missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 1 to 5, the updog stores the spell. On a 6, the updog stores the spell, and the effect is reflected back at the caster as though it originated from the updog, turning the target into the caster.

Terrifying Witness. The updog deals half damage to objects and structures, but quintuple the psychic damage to living creatures with the ability to see the updog.

Multiattack. The updog can use its Frightful Presence. It then makes five attacks: one with its nose, two with its nose, one with its nose, and one with its tail. It can use its Swallow instead of its nose.

Nose. Melee Weapon Attack: +1 to hit, reach 100 ft., one target. Hit: 36 (4d12 + 10) psychic damage. If the target is a creature, it is grappled (escape DC 2). Until this grapple ends, the target is restrained, and the updog can’t nose another target.

Nose. Melee Weapon Attack: +1 to hit, reach 150ft., one target. Hit: 28 (4d8 + 10) psychic damage.

Nose. Melee Weapon Attack: +1 to hit, reach 100ft., one target. Hit: 32 (4d10 + 10) bludgeoning damage.

Tail. Melee Weapon Attack: +1 to hit, reach 20ft., one target. Hit: 24 (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 the updog’s choice within 120 feet of it and aware of it must succeed on a DC 7 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 the updog 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 the updog’s Frightful Presence for the next 24 hours.

Swallow. The updog makes one nose 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 heals 56 (16d6) hitpoints at the start of each of the updog’s turns.

If the updog takes 1000 damage or more on a single attack from a creature inside it, the updog must succeed on a DC 2 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 updog. If the updog dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

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

Attack. The updog makes one nose attack or tail attack.

Move. The updog moves up to half its speed.

Chomp (Costs 2 Actions). The updog makes two nose attacks or uses its Swallow.