Amphibious.

The hag can breathe air and water.

Innate Spellcasting.

The hag's innate spellcasting ability is Charisma (spell save DC 12). She can innately cast the following spells, requiring no material components:

At will: dancing lights, minor illusion, vicious mockery

Mimicry.

The hag can mimic animal sounds and humanoid voices. A creature that hears the sounds can tell they are imitations with a successful DC 14 Wisdom (Insight) check.

Actions

Claws.

Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage.

Illusory Appearance.

The hag covers herself and anything she is wearing or carrying with a magical illusion that makes her look like another creature of her general size and humanoid shape. The illusion ends if the hag takes a bonus action to end it or if she dies.

The changes wrought by this effect fail to hold up to physical inspection. For example, the hag could appear to have smooth skin, but someone touching her would feel her rough flesh. Otherwise, a creature must take an action to visually inspect the illusion and succeed on a DC 20 Intelligence (Investigation) check to discern that the hag is disguised.

Invisible Passage.

The hag magically turns invisible until she attacks or casts a spell, or until her concentration ends (as if concentrating on a spell). While invisible, she leaves no physical evidence of her passage, so she can be tracked only by magic. Any equipment she wears or carries is invisible with her.

Lair Actions

The following lair actions are options for grandmothers and powerful aunties. Grandmothers usually have three to five lair actions, aunties usually only one (if they have any at all). Unless otherwise noted, any lair action that requires a creature to make a saving throw uses the save DC of the hag's most powerful ability.

On initiative count 20 (losing initiative ties), the hag can take a lair action to cause one of the following effects, but can't use the same effect two rounds in a row:

Until initiative count 20 on the next round, the hag can pass through solid walls, doors, ceilings, and floors as if the surfaces weren't there.
The hag targets any number of doors and windows that she can see, causing each one to either open or close as she wishes. Closed doors can be magically locked (requiring a successful DC 20 Strength check to force open) until she chooses to make them unlocked, or until she uses this lair action again to open them.

A powerful green hag might have the following additional lair action:

The hag creates an illusory duplicate of herself, which appears in its own space. As long as she can see her duplicate, the hag can move it a distance equal to her walking speed as well as make the illusion speak on her turn (no action required). The illusion has the same statistics as the hag but can't take actions or reactions. It can interact with its environment and even pick up and hold real objects. The illusion seems real in every way but disappears if it takes any amount of damage. Otherwise, it lasts until the hag dismisses it (no action required) or can no longer see it. If the hag uses this lair action to create a new duplicate, the previous one vanishes, dropping any real objects in its possession.

Regional Effects

Each hag's lair is the source of three to five regional effects; the home of a grandmother, an auntie, or a coven has more effects than the lair of a single hag, including some that can directly harm intruders. Any regional effect that requires a creature to make a saving throw uses the save DC of the hag's most powerful ability. These effects either end immediately if the hag dies or abandons the lair, or take up to 2d10 days to fade away.

The region within 1 mile of a grandmother hag's lair is warped by the creature's fell magic, which creates one or more of the following effects:

Birds, rodents, snakes, spiders, or toads (or some other creatures appropriate to the hag) are found in great profusion.
Beasts that have an Intelligence score of 2 or lower are charmed by the hag and directed to be aggressive toward intruders in the area.
Strange carved figurines, twig fetishes, or rag dolls magically appear in trees.

A powerful green hag creates one or more of the following additional regional effects within 1 mile of her lair:

Illusory duplicates of the hag appear in random places at random times (but never more than one in any given location). An illusory duplicate has no substance, but it looks, sounds, and moves like the hag. The hag can sense when one or more creatures are within 60 feet of her duplicate and can interact with them as if she were present and standing in the duplicate's space. If the illusory duplicate takes any damage, it disappears.
The region takes twice as long as normal to traverse, since the plants grow thick and twisted, and the swamps are thick with reeking mud.
Trees transform into awakened trees and attack when hostile intruders are near.

Green Hag