Damage Absorption. This creature can take no damage, if attacked it grows in size. The amount is determined by the damage total the attack would have dealt. If creature reaches Gargantuan size then this feature no longer takes effect, instead it can now be damaged and functions as a regular monster.

However, if reduced to 0 Hp instead of dying it shrinks back to the original form as it releases all power into the world, waiting for another opportunity to rise again.

1 - 15. (1/2 ft), 15 - 30. (1ft), 30+. (2ft)

Conqueror of Worlds. Gooze feasts on the power of those who attack. Each size allow it to gain different features and powers. For abilities and power look at the table bellow:

Small Size (2ft - 4ft).

AC 12 | Str: 10 | Dex: 14 | Con: 10 | Int: 10 | Wis: 8| Cha: 12

Original state, use stats as the are then apply the changes to the specific size. On this state it has proficiency on stealth check. This proficiency is lost when it enlarges.

Medium Size (4ft - 8ft). 

AC 12 | Str: 10 | Dex: 14 | Con: 12 | Int: 10 | Wis: 8| Cha: 12

Gains resistance to last damage dealt to it. Uses constitution as casting ability and can cast the following spells without using components: Misty Step (3/day), Invincibility (1/day).

Large Size (8ft - 16ft). 

AC 15 | Str: 14 | Dex: 14 | Con: 14 | Int: 10 | Wis: 8| Cha: 12

Gains another resistance based on the damage taken (or non if no other type of damage was applied to it),  can now also cast Suggestion (1/day) with a DC of 14. The command is passed telepathically and is more like a feeling than actual words.

Huge (16 - 32ft). 

AC 15 | Str: 16 | Dex: 14 | Con: 16 | Int: 10 | Wis: 8| Cha: 12

Gains immunity to one of the damage types it is resistant to. Spell DC increases to 16. Now can also cast Counterspell at 3rd level (1/day).

Gargantuan(33 ft).

AC 17 | Str: 18 | Dex: 14 | Con: 18 | Int: 10 | Wis: 8| Cha: 12

Now can also cast Danse Macabre (1/day) and gains Legendary Resistance (3/Day). If the it fails a saving throw, it can choose to succeed instead.

Multi-Attack. 

Creature can make 2 attacks. These can either be bite or peck. When becoming large or bigger it can make one additional attack.

Bite.

Melee Attack: +3 to hit, reach 5 ft., one target. Hit: 2 (1d4) piercing. (Small)

Melee Attack: +6 to hit, reach 5 ft., one target. Hit: 8 (2d4 + 2) piercing. (Medium)

Melee Attack: +8 to hit, reach 5 ft., one target. Hit: 12 (2d8 + 4) piercing. (Large)

Melee Attack: +12 to hit, reach 5 ft., one target. Hit: 18 (2d10 + 6) piercing. (Huge)

Melee Attack: +14 to hit, reach 10 ft., one target. Hit: 23 (2d10 + 8) piercing + 4(1d8) fire damage (Gargantuan)

Peck.

Melee Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) piercing. (Small)

Melee Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 4) piercing. (Medium)

Melee Attack: +8 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 6) piercing. (Large)

Melee Attack: +12 to hit, reach 5 ft., one target. Hit: 18 (2d10 + 8) piercing. (Huge)

Melee Attack: +14 to hit, reach 10 ft., one target. Hit: 23 (3d10 + 8) piercing. (Gargantuan)

Frightful Presence. Each creature of the Gooze choice that is within 120 ft. of the it and aware of it must succeed on a DC 13 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 the Gooze's Frightful Presence for the next 24 hours.

DC increases to 16 when Large and 19 when Huge or bigger.

Fire Breath (Recharge 5-6). [Only when in Gargantuan form] the Gooze exhales fire in a 60-foot cone. Each creature in that area must make a DC 21 Dexterity saving throw, taking 63 (18d6) fire damage on a failed save, or half as much damage on a successful one.

• Detect. Gooze makes a Wisdom (Perception) check.
• Peck. Gooze makes a peck attack.
• Wing Attack (Costs 2 Actions). Gooze beats its wings. Each creature within 10 ft. of the gooze must succeed on a DC 22 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. The Gooze can then fly up to half its flying speed.