Puddle Slime

False Appearance. While the ooze remains motionless, it is indistinguishable from a puddle.

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

Corrosive Form. Any non-magical weapon made of metal that hits the ooze 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. Non-magical ammunition made of metal that hits the ooze is destroyed after dealing damage.

The puddle slime can eat through 2-inch-thick, non-magical metal in 1 round.

Magical Resistance. The puddle slime has advantage on saving throws against spells and other magical effects.

Variant: Familiar. The puddle slime can enter into a contract to serve another creature as a familiar, forming a Telepathic Bond with its willing master. While the two are bonded, the master can sense what the puddle slime senses as long as they are within 1 mile of each other. While the puddle slime is within 10 feet of its master or merged with them, the master shares the puddle slime’s Magic Resistance trait. If merged with its master, the master shares its Corrosive Skin trait and Blindsight. If its master violates the terms of the contract, the puddle slime can end its service as a familiar, ending the Telepathic Bond.

Pseudopod. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) bludgeoning damage plus 6 (2d6) acid damage. If the target is wearing non-magical metal armor, its armor is partly corroded and takes a permanent and cumulative -1 penalty to the AC it offers. The armor is destroyed if the penalty reduces its AC to 10.