Homebrew
Amorphous. The mini-slop can move through a space as narrow as 1 inch wide without squeezing. Corrosive Form. Any weapon made of metal or wood that hits the mini-slop corrodes. On an attack roll of 1 or 2 against the mini-slop, the weapon drops a quality level, as if blocking a critical hit. Unless it's magical, if the weapon drops below Ruined, the weapon is destroyed. Nonmagical ammunition made of metal or wood that hits the mini-slop is destroyed after dealing damage. The mini-slop can eat through 2-inch-thick, nonmagical wood or metal in 1 round.
Pseudopod. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6+1) 1d6+1 bludgeoning damage plus 7 (2d6) 2d6 acid damage. On an attack roll of 19 or 20, armor worn by the target is partly dissolved and drops a quality level, as if being hit by a critical hit. Unless it is magical, the armor is destroyed if it drops below Ruined. Spit. Ranged Weapon Attack: +3 to hit, range 20/40 ft., one target. Hit: 4 (1d6+1) 1d6+1 bludgeoning damage plus 7 (2d6) 2d6 acid damage. On an attack roll of 19 or 20, armor worn by the target is partly dissolved and drops a quality level, as if being hit by a critical hit. Unless it is magical, the armor is destroyed if it drops below Ruined.