Blue Protodrake

Amphibious. The Protodrake can breathe in both air and underwater.

Echolocation. The Protodrake is blind, and relies on echolocation and ground vibrations to track it's prey. It has Blindsight out to 15 feet, and Tremorsense out to 30 ft., and it also has advantage on Wisdom (Perception) checks made to listen.

The Protodrake's outstanding auditory senses, however, are not perfect, leaving it particularly vulnerable to sound based illusion magics. It has disadvantage on Intelligence (Investigation) checks made to discern against auditory illusions and tricks.

Sonic Vulnerability. Whenever the Protodrake suffers Thunder damage, it must make a DC 15 Constitution saving throw, or become Blinded until the end of it's next turn.

Multiattack. The Protodrake makes two attacks: one to constrict and another with it's Sticky Tongue. If a creature that is Grappled by the Protodrake is within range, it may then attempt to Swallow the creature.

Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 22 (3d10+ 6) piercing damage.

Constrict. Melee Weapon Attack: +10 to hit, reach 5 ft., one Large or smaller creature. Hit: 17 (2d10 + 6) bludgeoning damage plus 17 (2d10 + 6) piercing damage. The target is Grappled if the Protodrake isn't already constricting a creature, and the target is Restrained until the grapple ends.

At the end of each of it's turns, a Grappled creature may attempt a DC 16 Athletics or Acrobatics check to escape the grapple, freeing itself on a success. 

Sticky Tongue. Melee Weapon Attack: +10 to hit, reach 20 ft., 1 target. Hit: The target is immediately Grappled, and if it is a Large or smaller creature, it must make a DC 18 Strength saving throw, or be pulled up to 10 feet towards the Protodrake. While Grappled in this manner, the creature is considered Restrained. At the end of each of it's turns, a Grappled creature may attempt a DC 16 Athletics or Acrobatics check to escape the grapple, freeing itself on a success. 

The Protodrake can only have one creature Grappled in this way at a time.

Stunning Discharge (Recharge 5-6). The Protodrake shoots a line of lightning from it's mouth that is 40 feet long, and 10 feet wide. Each creature in that line must make a DC 18 Constitution saving throw, or suffer 16 (3d10) lightning damage and be Stunned until the start of the Protodrake's next turn; they take half as much damage and are not Stunned on a successful save.

Swallow. The Protodrake makes a Bite attack against one creature that it is grappling. If the attack hits, the target is also swallowed, and the grapple ends. While swallowed, the creature is Blinded and Restrained, it has total cover against attacks and other effects outside the Protodrake, and it takes 21 (6d6) acid damage at the start of each of the Protodrake's turns. The Protodrake can swallow either: 1 Large creature, or up to 4 Medium or smaller creatures.

If the Protodrake suffers 40 or more damage from the swallowed creature(s) before the start of it's next turn, it must succeed on a DC 15 Constitution saving throw at the start of its next turn or regurgitate the swallowed creature(s), which fall Prone in space within 10 feet of the Protodrake. If the Protodrake dies, the swallowed creature(s) are no longer Restrained by it, and can escape from the corpse by using 15 feet of movement, exiting Prone.