Necrotic Vulnerability. If the fliezund takes 30 necrotic damage from a single attack or spell, it must succeed on a DC 23 Constitution saving throw or roots itself into the ground to refill its water supply for 1d2 rounds. While rooted, the fliezund is restrained and incapacitated, but has resistance to necrotic damage.
Multiattack. The fliezund makes two smash attacks. Smash. Melee Weapon Attack: +13 to hit, reach 20 ft.,one target. Hit: 22 (4d6 + 8) bludgeoning damage. Lunge. Melee Weapon Attack: +13 to hit, reach 20 ft., one target. Hit: 22 (4d6 + 8) bludgeoning damage and is pulled within 5 feet of the fliezund. If the target is Medium or smaller, it must succeed on a DC 19 Dexterity saving throw or be swallowed by the fliezund. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the fliezund, and it takes 21 (6d6) acid damage at the start of each of the fliezund's turns. If the fliezund takes 40 damage or more on a single turn from a creature inside of it, the fliezund must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate the swallowed creature, which falls prone in a space within 10 feet of the fliezund. Charge.The fliezund rushes forward, running 60 feet in a straight line. The fliezund cannot stop this charge. Any target in its path must succeed on a DC 19 Strength saving throw, taking 35 (10d6) bludgeoning damage on a failure, or half as much on a success. If a target fails its save, it is knocked prone. Frantic Backlash (Recharge 5–6). The fliezund uses one of the following abilities. Acid Rain. The fliezund spews a stream of acid upwards, which rains down in a 30-foot-radius, 40-foot-high cylinder centered on itself. Creatures in the area must make a DC 18 Dexterity saving throw. A target takes 45 (10d8) acid damage on a failure, or half as much on a success. Earth Rupture. The fliezund rips the ground in a 20-foo cube in front of itself. Targets in the area must make a DC 19 Dexterity saving throw, taking 49 (14d6) bludgeoning damage on a failure, or half as much on a success. Targets in a 20-foot cube behind the first cube can also make a DC 19 Dexterity saving throw, taking half damage on a failure from the flying earth, or a quarter as much on a success. Regardless of the save, targets in the first cube are thrown 20 feet away from the fliezund and are knocked prone.