Aboleth

The monster can breathe air and water.

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

While underwater, the monster is surrounded by mucus.
Constitution Saving Throw: DC 14, each in a - Emanation originating from the monster at the end of the monster's turn.
Failure: The target is cursed. Until the curse ends, the target's skin becomes slimy, the target can breathe air and water, and it can't regain Hit Points unless it is underwater.
While the cursed creature is outside a body of water, the creature takes damage at the end of every 10 minutes unless moisture is applied to its skin before those minutes have passed.

If a creature the monster can see communicates telepathically with the monster, the monster learns the creature's greatest desires.

If destroyed, the monster gains a new body in days, reviving with all its Hit Points in the Far Realm or another location chosen by the DM.

. . If the target is a Large or smaller creature, it has the Grappled condition (escape DC ) from one of four tentacles.

The monster makes two attacks and uses either or if available.

Wisdom Saving Throw: DC , one the monster can see within feet.
Failure: The target has the Charmed condition until the monster dies or is on a different plane of existence from the target. While Charmed, the target acts as an ally to the monster and is under its control while within feet of it. In addition, the monster and the target can communicate telepathically with each other over any distance.
The target repeats the save whenever it takes damage as well as after every 24 hours it spends at least 1 mile away from the monster, ending the effect on itself on a success.

Intelligence Saving Throw: DC , within feet. by the monster.
Failure: damage.
Success: damage.
Failure or Success: The monster gains the target's memories if the target is a Humanoid and is reduced to 0 Hit Points by this action.