Legendary Resistance (3/day). If the landwyrm fails a saving throw, it can choose to succeed instead.
Multiattack. The landwyrm can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws. Bite. Melee Weapon Attack: +12 to hit, reach 10ft., one target. Hit 18 (2d10 + 7) piercing damage plus 4 (1d8) acid damage. Claw. Melee Weapon Attack: +12 to hit, reach 5ft., one target. Hit 14 (2d6 + 7) slashing damage. Frightful Presence. Each creature of the landwyrms's choice that is within 120 feet of the landwyrm 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 landwyrm's Frightful Presence for the next 24 hours. Petrifying Breath (Recharges 5-6). The landwyrm exhales acidic adhesive in a 60-foot line that is 5 feet wide. Each creature in that line must make a DC 18 Constitution saving throw, taking 45 (10d8) acid damage on a failed save, or half as much damage on a successful one. If the saving throw fails by 5 or more, the creature begins to turn to stone and is restrained. The restrained creature must repeat the saving throw at the end of its next turn, becoming petrified on a failure or ending the effect on a success. The petrification lasts until the creature is freed by the greater restoration spell or similar magic.
The landwyrm can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The landwyrm regains spent legendary actions at the start of its turn. Detect. The landwyrm makes a Wisdom (Perception) check. Claw Attack. The landwyrm makes a claw attack. Erupting Stomp. The landwyrm forcefully slams the ground. Each creature within 15 feet of the landwyrm must succeed on a DC 19 Dexterity saving throw or take 14 (2d6+7) bludgeoning damage and be knocked prone. The landwyrm can then move up to half its movement speed.