Colossal Squig (5e Creature)
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Huge monstrosity, unaligned
Digestive Demise. When the squig dies, each creature within 10 feet of it must succeed on a DC 14 Dexterity saving throw or take 7 (2d6) acid damage as the squig collapses into a vile pool of guts, half-digested meat and digestive juices.
Extra Boingy. At the start of each of the squig's turns, roll 3d6. The squig gains a number of feet movement equal to the total to its speed this turn. If a triple is rolled, the colossal squig may make two bite attacks against a creature, or one bite attack and use its Swallow as an action.
Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 45 (6d12 + 6) piercing damage. If the target is a creature, it is grappled (escape DC 17). Until this grapple ends, the target is restrained, and the squig can't bite another target.
Spit. Ranged Weapon Attack: +6 to hit, range 30/60 ft., one target. Hit: 23 (6d6 + 2) acid damage.
Swallow. The squig makes one bite attack against a Medium or smaller creature it is grappling. If the attack hits, the target takes the bite's damage, the target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the squig, and it takes 28 (8d6) acid damage at the start of each of the squig's turns.