Amorphous. The cube can move through a space as narrow as 1 inch wide without squeezing.

Aquatic. The cube can breathe underwater and move through water without impediment.

Engulf. The cube moves up to its speed and enters a Large or smaller creature's space. The creature must make a DC 13 Dexterity saving throw or take 27 (6d8) acid damage. On a successful save, the creature is pushed out of the cube's space. A creature that starts its turn in the cube's space must make the saving throw or take the damage.

Split. When the cube reaches 0 hit points, it splits into two smaller cubes. Each new cube has hit points equal to one-half of the original cube's hit points, rounded down. If the original cube had 1 hit point, it forms two cubes, each with 1 hit point.

Underwater Camouflage. The cube has advantage on Dexterity (Stealth) checks made while underwater.

Pseudopod. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 2) acid damage.

Acidic Digestion. Any nonmagical object made of wood or metal that comes into contact with the cube is slowly dissolved. After 1 minute, the object is destroyed. Armor or a shield subjected to this effect is destroyed after 1 minute, unless it succeeds on a DC 13 Dexterity saving throw, taking half damage on a success.

Reactive Split. When a cube takes damage, it can use its reaction to split into two smaller cubes if it has at least 10 hit points.

The cube can take 1 legendary action, choosing from the options below. Only one legendary action option can be used at a time, and only at the end of another creature's turn. The cube regains spent legendary actions at the start of its turn.

Engulf. The cube uses its Engulf action.

Pseudopod Attack. The cube makes one pseudopod attack.

Move. The cube moves up to its speed without provoking opportunity attacks.