Becky

Amphibious.  Becky can breathe air and water.

Freedom of Movement. Becky ignores difficult terrain, and magical effects can't reduce its speed or cause it to be restrained. It can spend 5 feet of movement to escape from nonmagical restraints or being grappled.

Siege Monster. Becky deals double damage to objects and structures.

Multiattack. Becky makes five tentacle attacks, each of which it can replace with one use of Fling or Sting.

Tentacle. Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 20 (3d6 + 10) bludgeoning damage, and the target is grappled (escape DC 18). Until this grapple ends, the target is restrained. Becky has ten tentacles, each of which can grapple one target.

Fling. One Large or smaller object held or creature grappled by Becky is thrown up to 60 feet in a random direction and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 18 Dexterity saving throw or take the same damage and be knocked prone.

Sting. Melee Weapon Attack: +15 to hit, reach 30 ft., one creature. Hit: 10 (2d6 + 4) piercing damage, and the target must make a DC 17 Constitution saving throw, taking 10 (3d6) poison damage on a failed save, or half as much damage on a successful one. If the poison damage reduces the target to 0 hit points, the target is stable but poisoned for 1 hour, even after regaining hit points, and is paralyzed while poisoned in this way.

Frightful Presence. Each creature of Becky's choice that is within 120 feet of Becky 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 Becky's Frightful Presence for the next 24 hours.

Lightning Breath (Recharge 5–6). The dragon exhales lightning in an 60-­‐foot line that is 5 feet wide. Each creature in that line must make a DC 16 Dexterity saving throw, taking 55 (10d10) lightning damage on a failed save, or half as much damage on a successful one.