biggy c

Ooze Cube. The cube takes up its entire space. Other creatures can enter the space, but a creature that does so is subjected to the cube's Engulf and has disadvantage on the saving throw.

Creatures inside the cube can be seen but have total cover.

A creature within 5 feet of the cube can take an action to pull a creature or object out of the cube this includes the players inv. Doing so requires a successful DC 12 Strength check, and the creature making the attempt takes 10 (3d6) acid damage.

The cube can hold only one Large creature or up to four Medium or smaller creatures inside it at a time.

Transparent. Even when the cube is in plain sight, it takes a successful DC 15 Wisdom (Perception) check to spot a cube that has neither moved nor attacked. A creature that tries to enter the cube's space while unaware of the cube is surprised by the cube.

acid eater

immune to metal since your made of acid if some one attacks you with say a metal sword this means you take 0 damage and the metal dissolves and they become grappled they must make a dc14 strength save to escape. this sub variant comes with weakness to fire and magic (except acid and water damage)  taking double damage to both.

Pseudopod. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 10 (3d6) acid damage.

Engulf. The cube moves up to its speed. While doing so, it can enter Large or smaller creatures' spaces. Whenever the cube enters a creature's space, the creature must make a DC 12 Dexterity saving throw.

On a successful save, the creature can choose to be pushed 5 feet back or to the side of the cube. A creature that chooses not to be pushed suffers the consequences of a failed saving throw.

On a failed save, the cube enters the creature's space, and the creature takes 10 (3d6) acid damage and is engulfed. The engulfed creature can't breathe, is restrained, and takes 21 (6d6) acid damage at the start of each of the cube's turns. When the cube moves, the engulfed creature moves with it.

An engulfed creature can try to escape by taking an action to make a DC 12 Strength check. On a success, the creature escapes and enters a space of its choice within 5 feet of the cube.

suicidal children

you can use 1 mass point to create a smaller version of your self who locks on to a creature doing 1d6 of acid damage  a turn until pulled of which is a dc14 strength save. at mass 5 its a small and 7 its a medium at 9 its large and 12 its a huge adding 1d4 of damage per size

acid spit ball

you can use 0.5 of your mass to spit part of your self at an enemy doing 1d8 damage 

engulf body

you can use the next turn to eat a body adding 1 to your mass counter

unstable roll

you can use your turn to roll 10 foot if someone's in the space there engulfed you can then make a dc15 dex roll to move another 5 foot and if theres a creature there they get engulfed if there's space  

if you die you explode the damage is different depending on size 1d10 if small 2d10 if medium 3d10 if large 410 if huge and 5d10 if gargantuan