Colossal Squig

Standing Leap. The Squig can leap 30ft by sacrificing 5ft of movement speed. 

Crash Landing. If the Squig Lands on the same space as a creature they fall prone. 

Multi Attack. When taking the attack action the Colossal Squig makes two bite attacks and one stomp attacks. One use of Bite can be substituted for swallow.  

Bite. Melee Attack Roll: +11 to hit, reach 5ft., 1 target, Hit: 27 (5d6+10) piercing damage and a creature is grappled. while a creature is grappled in this way they gain the Clumsy and Enfeebled conditions. If a creature that is small or smaller is bit by this attack, they are automatically swallowed. 

Stomp. Each creature in a 15ft radius from the squig must make a DC 18 DEX save or take 13 (3d6+5) bludgeoning damage and drop whatever they are holding in their hands. 

Swallow. Roll a Bite attack and instead of taking damage the creature is swallowed by the Squig and takes 36 (8d8) acid damage at the start of its turns. While swallowed a creature is restrained and has full cover from all attacks and effects. 

Regurgitate (Recharge 5-6). Each creature caught in a 45ft cone must make a DC 17 DEX save or take 36 (8d8) acid damage and begin burning (1d8 acid). For any creatures currently swallowed by the Squig are harmless dropped prone within 10ft of the squig. 

The Colossal Squig has 3 legendary actions that it can use to activate one of the following actions at the end of another creatures turn. Regaining all expended uses at the start of its next turn. 

Rolling (costs 1 action). The Colossal Squig moves up to its movement speed

Chomp (costs 1 action). The Colossal Squig makes one Bite attack against a creature it can see. 

Belch (costs 2 actions). The Colossal Squig belches and releases a toxic cloud affecting all creatures within 30ft. Each creature must make a DC 14 WIS save or be poisoned and take 18 (4d8) poison damage. Save ends.