Amphibious. The hag can breathe air and water.

Coven Magic. While within 30 feet of at least two hag allies, the hag can cast one of the following spells, requiring no Material components, using the spell’s normal casting time, and using Intelligence as the spellcasting ability (spell save DC 12): Augury, Find Familiar, Identify, Locate Object, Scrying, or Unseen Servant. The hag must finish a Long Rest before using this trait to cast that spell again.

Legendary Resistance (2/Day, or 3/Day in Lair). If the hag fails a saving throw, it can choose to succeed instead.

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

Multiattack. The hag makes two Claw attacks.

Claw. Melee Attack Roll: +7, reach 5 ft. Hit: 8 (1d8 + 4) Slashing damage plus 3 (1d6) Poison damage.

Spellcasting. The hag casts one of the following spells, requiring no Material components and using Wisdom as the spellcasting ability (spell save DC 14, +6 to hit with spell attacks):

At Will: Bane, Dancing Lights, Disguise Self (24-hour duration), Invisibility (self only, and the hag leaves no tracks while Invisible), Minor Illusion, Ray of Sickness (level 3 version)
2/Day Each: Hypnotic Pattern, Polymorph
1/Day Each: Dominate Monster, Modify Memory

Tongue Twister. The hag casts Counterspell in response to that spell’s trigger, using the same spellcasting ability as Spellcasting.

Legendary Action Uses: 2 (3 in Lair). Immediately after another creature’s turn, the hag can expend a use to take one of the following actions. The hag regains all expended uses at the start of each of its turns.

Hag’s Swipe. The hag makes one Claw attack.

Witch Step. The hag magically teleports to an unoccupied space it can see within 60 feet of it.