Armored Ooze

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

Corrode Metal. Any nonmagical/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 by 5, or more the weapon is destroyed. Nonmagical or magical ammunition made of metal that hits the ooze is destroyed after dealing damage.

The ooze can eat through 2-inch-thick, nonmagical metal in 1 round and magical in 2 rounds.

Liquid Defense. As combat continues the Armored Ooze's defense changes each round. At the beginning of each of the Armored Ooze's turn roll 1d20 that roll becomes the Armored Ooze's defense for that turn.

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

Pseudopod. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) bludgeoning damage plus 7 (2d6) acid damage, and if the target is wearing nonmagical 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.

Absorb Metals. The Armored Ooze can as a bonus action absorb any corrode it has done that turn. Healing itself 1d6 damage for every 1 point of damage it has dealt that turn. In addition if it has destroyed any metal ammunition that round it can heal 1d4 damage for each piece of ammunition destroyed.

Corrosive Grip. If the Armored Ooze attacks with its Pseudopod and hits a creature with magical armor, then it attempts to grapple. The target gets a Dex save to attempt to dodge the grapple DC 18+, upon failing it is grappled. Upon a success it is not grappled. If successfully grappled every round they can make a Str save to attempt to break the grapple DC 19+, if they fail they remain grappled as well all their weapons and armor are corroded and take a permanent and cumulative -1 penalty to the AC it offers. The Armor is destroyed if the penalty reduces its the AC to 8.

The Armored Ooze moves toward anything that seems like a new material.

The Armored Ooze has 3 legendary actions it can use.

Quick Blitz Slime. As a legendary action the Armored Ooze will change its body to quickly cover ground in a battle with a particularly slippery target. It will use the dash action for the cost of a legendary action.

Armor Switch. If the Armored Ooze is hit 2 time in a round it can use a legendary action to roll its new AC.

Binding Grip. If the Armored Ooze has a creature grappled it can use a legendary action the do an attack action with a Pseudopod holding the grappled creature at a target with 5 feet of it. The grappled creature can make a strength save, at disadvantage, to break the grapple DC 19+. Upon a failure the grappled creature is used as bludgeoning instrument and slammed against the target dealing 3d6+1 bludgeoning damage to each. Upon a success the creature has freed itself but the Pseudopod attack action happens as a normal attack.