Ooze Master

A creature that touches the Ooze Master or hits it with a melee attack while within 5 feet of it takes 9 (2d8) acid damage. Any nonmagical weapon that hits the Ooze Master 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 that hits the Ooze Master is destroyed after dealing damage.

The Ooze Master can eat through 2-inch-thick, nonmagical wood or metal in 1 round.

When the Ooze Master casts a spell with a casting time of 1 action, it can make one pseudopod attack as a bonus action.

The Ooze Master can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Melee Attack Roll: +7 to hit, reach 10 ft., one target. Hit: 13 (3d6 + 3) bludgeoning damage plus 10 (3d6) acid damage.

If a creature the Ooze Master can see makes an attack roll against it while within 30 feet of it, the Ooze Master can use a reaction to divert the attack if another creature is within the attack's range. The attacker must make a DC 15 Wisdom saving throw. On a failed save, the attacker targets the creature that is closest to it, not including itself or the Ooze Master. If multiple creatures are closest, the attacker chooses which one to target. On a successful save, the attacker is immune to this Instinctive Charm for 24 hours. Creatures that can't be charmed are immune to this effect.

The Ooze Master is a 9th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 15, +7 to hit with spell attacks). It has the following wizard spells prepared:

Cantrips: acid splash, friends, mage hand, poison spray

Level 1 (4 slots): charm person, detect magic, magic missile, ray of sickness

Level 2 (3 slots): detect thoughts, Melf's acid arrow, suggestion

Level 3 (3 slots): fear, slow, stinking cloud

Level 4 (3 slots): confusion, Evard's black tentacles

Level 5 (1 slots): cloudkill