Chief Guh (Gluttony Demon)

Multiattack. The giant makes two greatclub attacks.

Greatclub. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 18 (3d8 + 5) bludgeoning damage.

Rock. Ranged Weapon Attack: +8 to hit, range 60/240 ft., one target. Hit: 21 (3d10 + 5) bludgeoning damage.

(Gluttony Form)
Multiattack. The giant makes two bite attacks.

Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 22 (3d8 + 9) piercing damage. If the target is a Large or smaller creature, it must succeed on a DC 19 Dexterity saving throw or be swallowed by Gluttony. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside Gluttony, and it takes 21 (6d6) acid damage at the start of each of Gluttony's turns.

If Gluttony takes 30 damage or more on a single turn from a creature inside it, Gluttony must succeed on a DC 21 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of Gluttony. If the Gluttony dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 20 feet of movement, exiting prone.

Repulsive Bile.  Gluttony exhales vomit from it's second mouth in a 30-foot cone. Each creature in that area must succeed on a DC 19 Dexterity saving throw, taking 54 (12d8) acid damage on a failed save, or half as much damage on a successful one. On a failed save, the creature is coated in bile and at the start of each of its turns it must make a DC 16 Constitution saving throw, taking 2d8 acid damage on a failed save or half on a successful one.

(Mythic Actions)
oh lord she comin: Gluttony can move up to 15ft

Ceaseless Hunger (costs 2 actions). Gluttony opens both of its mouths, inhaling sharply and causing a violent vacuum to form. Creatures within 80 ft. in the direction that Gluttony is facing must make a DC 24 Strength saving throw or be sucked into the vortex. Creatures take 8d8 force damage and make a DC 15 Dexterity saving throw or are automatically swallowed by Gluttony on a failed save, or half as much damage and remain in place on a successful one. Gluttony may use this ability during its turn as an action or at initiative count 20. 

When Chief Guh reaches below 75 health, on initiative count 20 she stands and throws an angry fit. Stomping around angrily and demanding to consume all. Her thrashing and stomping causes the floor to collapse through both the 2nd and 1st floors as Chief Guh and player descend into a cavernous pit with walls 200ft tall. Players impact is cushioned by the fat of Chief Guh and take no damage. 

Guh quickly stands and angrily explodes in demonic power as her aspect of Gluttony forms. Regaining up to 150 health. 

Earth-shaker. A tremor shakes the ground in a 60-foot radius around Gluttony when it moves. Each creature other than Gluttony on the ground in that area must succeed on a DC 24 Strength saving throw or be knocked prone

Gluttonous Fat. Any time Gluttony is targeted by a magic missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 1 to 5, the damage is halved. On a 6, Gluttony is unaffected, and the spell is consumed as gluttony regains half of the damage it would of inflicted. 

Regeneration. Gluttony digests some of the nutrients in it's bottomless stomach and regains 20 hit points at the start of its turn if it has at least 1 hit point.

Tunneler. Gluttony can burrow through solid rock and leaves a 20-foot-diameter tunnel in its wake.