Heated Body. A creature that starts its turn while touching the tatzelwurm or that hits it with a melee attack while within 5 feet of it takes 7 (2d6) fire damage.

Keen Sight and Smell. The tatzelwurm has advantage on Wisdom (Perception) checks that rely on sight or smell.

Legendary Resistance (2/day). If the tatzelwurm fails a saving throw, it can choose to succeed instead.

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

Pack Tactics. The tatzelwurm has advantage on an attack roll against a creature if at least one of the tatzelwurm's allies is within 5 feet of the creature and the ally isn't incapacitated.

Pounce. If the tatzelwurm moves at least 20 feet straight toward a creature and then hits it with a claw attack on the same turn, that target must succeed on a DC 17 Strength saving throw or be knocked prone. If the target is prone, the tatzelwurm can make one constrict attack against it as a bonus action.

Multiattack. The tatzelwurm makes three attacks: two with its claws and one with its bite.

Bite. Melee Weapon Attack: +9 to hit, one target, reach 5 ft. Hit: 11 (1d12+5) piercing damage. The target must make a DC 17 Constitution saving throw, taking 24 (7d6) poison damage on a failure or half as much on a success. In addition, on a failure, the target is poisoned for one minute. It can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Claw. Melee Weapon Attack: +9 to hit, reach 5 ft, one target. Hit: 9 (1d8+5) slashing damage plus 7 (2d6) fire damage.

Constrict. Melee Weapon Attack: +9 to hit, reach 5ft., one target. Hit: 10 (1d10+5) bludgeoning damage plus 7 (2d6) fire damage and the target is grappled (escape DC 17) unless it is huge or larger. While grappled, the target also is restrained and the tatzelwurm cannot constrict another target.

Fire Breath (Recharge 5–6). The tatzelwurm breathes fire in a 30-foot cone. Each creature in that area must make a DC 16 Dexterity saving throw, taking 42 (12d6) fire damage on a failure or half as much on a success.

The  tatzelwurm can take 2 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 tatzelwurm regains spent legendary actions at the start of its turn.

Claw. The tatzelwurm makes an attack with its claw.

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

Prowl. The tatzelwurm moves up to its speed without provoking opportunity attacks and takes the hide action.

Poison Spit (Costs 2 Actions). The tatzelwurm spits poison at a creature it can see within 30 feet of it. The target must make a DC 17 Constitution saving throw, taking 24 (7d6) poison damage on a failure or half as much on a success. In addition, on a failure, the target is poisoned for one minute. It can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.