Amorphous. The pudding can move through a space as narrow as 1 inch wide without squeezing.   Corrosive Form. A creature that touches the pudding or hits it wiht a melee attakc while within 4 feet of it takes 4 (1d8) 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 drestroyed. 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   Spider Climb. The pudding can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.