Juiblex

Any creature other than an Ooze that starts its turn within 10 feet of Juiblex must succeed on a DC 21 Constitution saving throw or be Poisoned until the start of the creature's next turn.

If Juiblex fails a saving throw, it can choose to succeed instead.

Juiblex has advantage on saving throws against spells and other magical effects.

Juiblex regains 20 hit points at the start of its turn. If it takes fire or Radiant damage, this trait doesn't function at the start of its next turn. Juiblex dies only if it starts its turn with 0 hit points and doesn't regenerate.

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

Juiblex makes three Acid Lash attacks.

Melee or Ranged Weapon Attack +14 to hit, reach 10 ft. or range 60/120 ft., one target. 21 (4d6 + 7) Acid damage. Any creature killed by this attack is drawn into Juiblex's body, where the corpse is dissolved after 1 minute.

Juiblex spews out a corrosive slime, targeting one creature that it can see within 60 feet of it. The target must succeed on a DC 21 Dexterity saving throw or take 55 (10d10) Acid damage. Unless the target avoids taking all of this damage, any metal armor worn by the target takes a permanent −1 penalty to the AC it offers, and any metal weapon the target is carrying or wearing takes a permanent −1 penalty to damage rolls. The penalty worsens each time a target is subjected to this effect. If the penalty on an object drops to −5, the object is destroyed. The penalty on an object can be removed by the Mending spell.

Juiblex makes one Acid Lash attack.

Melee Weapon Attack +14 to hit, reach 10 ft., one creature. 21 (4d6 + 7) Poison damage, and the target is slimed. Until the slime is scraped off with an action, the target is Poisoned, and any creature, other than an Ooze, is Poisoned while within 10 feet of the target.