Crude Pudding

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

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 pudding's Trap and has disadvantage on the saving throw.

Creatures trapped by the pudding can be seen but are restrained.

A creature within 5 feet of the cube can take an action to pull a creature or object out of the cube. Doing so requires a successful DC 12 Strength check, and the creature making the attempt  is subjected to the pudding's Trap.

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

Spider Climb. The pudding can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Pseudopod. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit:10 (3d6) bludgeoning damage. In addition, a non-magical weapon is subjected to the pudding's Trap and has disadvantage on the saving throw.

Trap. The pudding moves up to its speed. While doing so, it can enter Large or smaller creatures' spaces. Whenever the pudding 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 pudding. A creature that chooses not to be pushed suffers the consequences of a failed saving throw.

On a failed save, the pudding enters the creature's space, and the creature is trapped. The trapped creature is restrained. When the pudding moves, the trapped creature moves with it.

A trapped 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 pudding.

Split. When a pudding that is Medium or larger is subjected to lightning or slashing damage, it splits into two new puddings if it has at least 10 hit points. Each new pudding has hit points equal to half the original pudding's, rounded down. New puddings are one size smaller than the original pudding.

Ignite. When a pudding that is Medium or larger is subjected to fire damage, it ignites and every surrounding creature who fails a 15 Dexterity check receives 1d10 fire damage (including the pudding). A creature that is trapped suffers the consequences of a failed saving throw. After the ignition, the pudding size is one size smaller.