Monster Manual, page 179
Amphibious. The hag can breathe air and water. Horrific Appearance. Any humanoid that starts its turn within 30 feet of the hag and can see the hag's true form must make a DC 11 Wisdom saving throw. On a failed save, the creature is frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if the hag is within line of sight, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the hag's Horrific Appearance for the next 24 hours. Unless the target is surprised or the revelation of the hag's true form is sudden, the target can avert its eyes and avoid making the initial saving throw. Until the start of its next turn, a creature that averts its eyes has disadvantage on attack rolls against the hag.
Claws. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) slashing damage. Death Glare. The hag targets one frightened creature she can see within 30 feet of her. If the target can see the hag, it must succeed on a DC 11 Wisdom saving throw against this magic or drop to 0 hit points. Illusory Appearance. The hag covers herself and anything she is wearing or carrying with a magical illusion that makes her look like an ugly creature of her general size and humanoid shape. The effect 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 no claws, but someone touching her hand might feel the claws. Otherwise, a creature must take an action to visually inspect the illusion and succeed on a DC 16 Intelligence (Investigation) check to discern that the hag is disguised.
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:
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:
Coastal, Underwater