Black Pudding Souffle

Air Form. The elemental can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 inch wide without squeezing.

A black pudding Souffle secretes an areosolized digestive acid that dissolves organic material and metal quickly, but does not affect stone. any creature or object within a 10ft radius must make a Con save DC 14 or take 2d6 acid damage. non magical objects automatically fail and take this damage as thought they were vulnerable. 

Corrosive Form. 

A creature that touches the pudding or hits it with a melee attack while within 5 feet of it takes 4 (1d8) acid damage. Any nonmagical weapon made of metal or wood that hits the pudding corrodes. After dealing damage, the weapon takes a permanent and cumulative −1 penalty to damage rolls. If its penalty drops to −5, the weapon is destroyed. Nonmagical ammunition made of metal or wood that hits the pudding is destroyed after dealing damage. The pudding can eat through 2-inch-thick, nonmagical wood or metal in 1 round.

Symbiotic Partnership: air elemental and black pudding putting aside the differences to become an unstoppable creature, as such this monster is considered to be two separate beings sharing the same space, with their own actions per round, though they share the same hit points, movement and senses. when using this monster also roll initiative for the large air elemental and an elder black pudding respectfully. 

team Jam Slam!: the black Souffle slams into the opponent with the fury that only an unlikely alliance can achieve, until the end of Black Souffle's next turn, the Air elemental gains 2d6 acid damage to any of their attacks, and the Elder Black Pudding receives a range increase to its attacks of 15ft. 

Bubble Launch: fire a single bubble of Black Pudding at high velocity, 30ft, +8 attack, 1d10+5 bludgeoning and 2d6 acid damage, the target rolls a Strength save DC 12 or have a 1 hit point Black Pudding be grappling them.

Bubble Bullet Blitz: (Recharge 5-6) the Black Souffle  swirles around, creating dozens of small bubbles of black pudding and launching them in a 30ft radius. roll 2d10, and place Black Puddings around the field, each with 1 hit point.

Split: Slashing and piercing weapons deal no damage to a black pudding Souffle. Instead, the creature can choose to as a Reaction to split into an identical pudding, with 1/2 of the original’s current hit points (round down), using the Black Souffle's hp. A Souffle with 10 hit points or less cannot be further split and are no longer combined if reduced to 0 hit points.