Flumph

Advanced Telepathy. The flumph can perceive the content of any telepathic communication used within 60 feet of it, and it can't be surprised by creatures with any form of telepathy.

Prone Deficiency. If the flumph is knocked prone, roll a die. On an odd result, the flumph lands upside-down and is in capacitated. At the end of each of its turns, the flumph can make a DC 10 Dexterity saving throw, righting itself and ending the incapacitated condition if it succeeds.

Telepathic Shroud. The flumph is immune to any effect that would sense its emotions or read its thoughts, as well as all divination spells.

Tendrils. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 4 (1d4 + 2) piercing damage plus 2 (1d4) acid damage. At the end of each of its turns, the target must make a DC 10 Constitution saving throw, taking 2 (1d4) acid damage on a failure or ending the recurring acid damage on a success. A lesser restoration spell cast on the target also ends the recurring acid damage.

Stench Spray (1/Day). Each creature in a 15-foot cone originating from the flumph must succeed on a DC 10 Dexterity saving throw or be coated in a foul-smelling liquid. A coated creature exudes a horrible stench for 1d4 hours. The coated creature is poisoned as long as the stench lasts, and other creatures are poisoned while within 5 feet of the coated creature. A creature can remove the stench on itself by using a short rest to bathe in water, alcohol, or vinegar.