Amphithere

Multiattack. The amphithere can use its Frightening Presence. It can then make 3 attacks: two with either its claws or its bite, and one with its tail.

Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 9 (1d10 + 4) piercing damage and 5 (1d10) poison damage. 

Claws. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 11 (2d6 + 4) slashing damage. 

Tail. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 9 (1d10 + 4) piercing damage, 5 (1d10) poison damage and the target must make a DC 15 Constitution saving throw, on a failed save the target's hit point maximum is reduced by an amount equal to the poison damage taken, and the Amphithere regains hit points equal to that amount.

Constrict. Melee Weapon Attack: +8 to hit, reach 10 ft., one Large or smaller creature. Hit: 11 (2d6 + 4) bludgeoning damage, and the target is grappled (escape DC 15). Until this grapple ends, the target is restrained, and the Amphithere can't constrict another target.

Frightful Presence. Each creature of the amphithere's choice that is within 120 feet of the amphithere and aware of it must succeed on a DC 14 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 amphithere's Frightful Presence for the next 24 hours. 

Poison Breath (Recharge 5-6). The amphithere exhales poisonous gas in a 40-foot cone. Each creature in that area must make a DC 15 Constitution saving throw, taking 45 (13d6) poison damage on a failed save, or half as much damage on a successful one.