Acid Absorption. Whenever the arcane ooze is subjected to acid damage, it takes no damage and instead regains a number of hit points equal to the acid damage dealt.
Amorphous. The ooze can move through a space as narrow as 1 inch wide without squeezing.
Corrode Metal. Any nonmagical 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. Nonmagical 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.
Corrosive Form. A creature that touches the arcane ooze or hits it with a melee while within 5 feet of it takes 5 (2d6) acid damage.
Magic Resistance. An arcane ooze has advantage on saving throws against spells and other magical effects.
Multiattack. The ooze makes two pseudopod attacks and, if it can, uses its Spell Siphon.
Pseudopod. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage plus 13 (3d8) 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.
Spell Siphon (Recharge 5-6). The arcane ooze can attempt to siphon a spell from a creature with spell slots within 60 ft. The creature must succeed on a DC 14 Constitution saving throwing. If they fail, they lose a spell slot of the highest level they have available. In addition, the arcane ooze regains a number of hit points equal to four times the level the level of the spell slot (cantrips heal 2 hit points), and the target creature takes 7 (2d8) psychic damage.