Sewn Sisters
The Sewn Sisters are major villains who might try to creep into the camp during the jungle journey of the heroes to attempt to steal some of their hair or blood, which can be used to make a demented clone of the character (see "Cage" on page 180 of the Tomb of Annihilation book).
Here are night time encounters that can be used for each hag's attempt to steal blood or hair during the night.
(MM pg 178) Night Hag: AC 17, HP 112, Spd 30, +6 to hit, 13 (2d8+4) slashing dmg.
Change Shape. Polymorph into a small or medium female humanoid.
Etheralness. Enter or exit the ethereal. Must have her heartstone to do so.
1/day Nightmare haunting. Touch a sleeper from the ethereal, giving them dreadful visions. Gain no benefits from its rest. HP Max is reduced by 5 (1d10).
Has a +6 to stealth.
Spells: (at wilI) magic missile, (2/day) plane shift (self only), ray of enfeeble, sleep.
Peggy Deadbells
The group is traveling through the jungle. It is around 3 PM. Up ahead, you hear the roar of a dinosaur and the sound of a female voice speaking arcane words. A blue glow lights up the trees ahead of you for a
moment.
The group will see a tabaxi trying to fend off a hadrosaurus (pg 229). The tabaxi has a peg leg. If the group helps her, she thanks them.
Ringing Bells. She says her name is Ringing Bells. In truth, she is Peggy Deadbells, shapeshifted. She says that she was with the Company of the Yellow Banner, but got separated when a t. rex attacked them.
She will give the group some useful information to gain their trust, which could include a description of the trickster gods, a topic she pretends to be interested in.
Taking Watch. She will try to join up with the group. She'll offer to take watch at night. If the group lets her, she's got it made. She'll pluck some hair and then give one of the group a nightmare haunting. The nightmare involves the character watching a hag pull the soul from a little girl and stuffing it into a doll made of straw. This is the origin of Strawbundle, one of the dolls on pages 179-180 of Tomb of Annihilation.
Sneaking Around. If she doesn't take watch, she'll get up at midnight and make a stealth check (she has +6). She'll try to cast sleep on the person keeping watch. If that fails, she'll cackle and assume her true form, that of a night hag with a peg leg and a necklace of chattering teeth. She cackles, spewing yellow gas from her nose into the character's face. She'll swipe at the hero, hoping to get some blood on her claws. Then she'll go ethereal and head home.
Baggy Nanna
The group is camped and eating dinner. There's a rustling in the brush. It's a dog! A tenier, to be exact. It is missing fur in a number of spots, and looks like it is sick.
It will try to get a character to follow it. It leads the character to a hidden grove of fresh banana trees. It will try to earn the group's trust. It will repeatedly lead a character into the jungle and bring them to something useful - wood for a fire or a dead body that has useful stuff on it.
The Shadowy Grove. Eventually, it leads a character to an area of dark trees. Standing in the shadows is what looks like a 5-foot tall stump. The top of it is wiggling. It's not a tree. It's Baggy Nanna, with her hood wiggling because there's a viper and a cockatiel in it. She lunges forward and tries to strangle the character to death.
Strangulation. Opposed Strength check. She has a +4 to the roll. If the character fails, they can hold their breath for their constitution modifier +1 rounds. When that time runs out, the character drops to 0. She doesn't want the character dead. She wants them unconscious, so she can haunt their nightmares. The character has a nightmare where they are in a sack that is thrown into the ocean. There are other creatures in it with them - some kind of bird, a venomous snake, and a vicious canine. The character is tom to shreds and wakes up - Baggy Nanna and her animals are nowhere to be seen. She snatched some hair and she's gone.
Widow Groat
The group comes upon an area thick with branches of vibrant trees. The branches are in the way - they'll need to be chopped to proceed. Regardless of how they handle this situation, a woman made of wood steps from behind a tree. A beautiful woman made of wood steps from behind a tree. She says "Please! You mustn't harm my trees! The undead horde has done so much damage to my kind. Have mercy upon us."
The Wimba Bride. She says her name is The Wimba Bride (wimba being a type of jungle tree). She will lead the heroes to some ryath root (page 205) and explain that it can give them strength, but to consume just one root or it will make you sick (true). She will leave them in a pleasant manner, acting as if she is too shy to spend any more time with mortals.
When the group makes camp for the night, she timidly greets them from the edge of the forest. She is holding a bowl made of leaves. In it is soup she made from "Tonga Leaves" (which is a made-up thing, but as far as the group is concerned, it could be a "new discovery" from ToA pg 205).
The Brew. This isn't a natural herbal soup. It is a greenish-black brew from the cauldron on page 180 of Tomb of Annihilation. Anyone who tastes it is stunned for 1d10 minutes. Those who are stunned experience horrid dreams sent by the atropal (ToA pg214) - a vision of their soul being sucked right out of their own mouth and drawn into the face of a massive, hovering god-thing.
The "Wimba Bride" will assume her true form - Widow Groat, a hag with gold coins over her eyes and ants crawling out of her skull. Her ants swarm over the bodies of those who are stunned. The ants will draw blood from them.
Fighting Groat. If any heroes are conscious, she'll send a horde of ants skittering out of her head toward them. The ants are harmless, but the group won't know that. Once the group is ready to mount an attack, she'll try to bite a chunk of bloody flesh out of a character and vanish into the ethereal plane.
Not Over. Later that night, she'll return and try to haunt the dreams of the character she interacted with the most. The nightmare will involve the character lying immobile, but conscious. They can only watch as the hag drills a hole into their head. The widow's ants march from the hag's body into the freshly-drilled hole in the hero's skull.
If None Succeed
If none of the hags get hair or blood, it's no big deal. The main goal of this was to get the group familiar with the hags and anticipate fighting them..
The clones are cool, so if you want to use them but your hags failed to get hair or blood, you can do the following. After the group has a bloody battle in the jungle or in Omu and they stagger off to someplace safe, one of the hags appears from the ethereal plane and dips vials into the pools of blood on the ground. Anybody who was injured in the battle now has a clone.
Killing Baggy Nanna
Baggy Nanna is one of the Sewn Sisters (see ToA pg180). It is probable that many players will want to see what's under Baggy Nanna's hood. What follow is one possible answer to that question.
As described in the adventure, Baggy Nanna has a sack sewn to her head. There are animals in the sack, and dark eyehole in the bag.
The Official Answer
I asked Will Doyle, the author who created the Sewn Sisters, what the deal was. He told me that Baggy Nanna was inspired by an old form of punishment called poena cullei ("penalty of the sack").
Poena Culle is what happens if you are found guilty of killing your parents according to wikipedi: "The punshment consisted of being sewn up in a leather sack, sometimes with an assortment of live animals, and then being thrown into water."
I also asked him what's under the sack. His response: "I'd say it's her bloated, drowned face, fused horribly with three animals."
Surreal Version
Here's an elaborate scenario you can run if a character wants to get a look under the hood. If a character rips the bag or is able to tear the stitching from her neck, read: Suddenly, an overwhelming suction force drags you into the void in the sack. You are suddenly in total darkness. You can feel that you are underwater, sinking fast. You sense that there are other creatures in the sack with you.
This is a magic failsafe, a way for Baggy Nanna to be reborn. The character is in a demiplane of swamp water. If any of the animals in the sack manage to hit the character, they draw the needed blood to trigger the rebirth.
The creatures in the sack: A cockerel, a viper, and a terrier. All of them have darkvision 60 ft. When one of them hits the character, the runes being written on Baggy's remains also appear on the character's chest.
Terrier (Dire WoIf, MM pg 321) AC 14, HP 37, Spd 50, +5 to hit, 10 (2d6+2) piercing damage and strength save DC 13 or be knocked prone.
Cockerel AC 10, HP 1, +1 to hit, 1 dmg. Fly 30, Spd 20
Viper (modified constrictor snake, MM pg 320) AC 12, HP 13, Spd 30, Swim 30, +4 to hit, 5 (1d6+2 piercing dmg and DC 11 Con save, taking 10 (3d6) poison dmg on a failed save, or half as much dmg on a successful save.
Escaping the sack. The sack is magically reinforced. Water trickles in, taking 3 rounds to fill completely.
Cutting the Sack Open. The sack has an AC of 5, and has 20 hit points. It has a DR of 10, meaning that a character has to do at least 10 points of damage in a single attack to do any damage at all. Immune: poison, psychic, fire.
Swimming. Once out of the bag, the character will see a glow up above the surface of the water. They'll need to swim 100 feet up. Remember, the viper can swim, too. The other animals will drown unless rescued. Hovering half a foot above the surface of the water is a burbling, bubbling green portal. This portal is one-way. Through it, the character can see into the room where Nanna's corpse is. The character can pass through the portal as part of a move action. The character will emerge from Nanna's corpse as described below.
The Corpse
Baggy Nanna has three goblin fingers on her person. Once Nanna is slain, these fingers float in the air and frantically begin carving runes on Baggy Nanna's flesh, drawing dark blood. A DC 15 Intelligence (Arcana) check reveals that these runes are a way for Nanna's corpse to "birth" two creatures: The character who has been drawn in, and something else.
Emerging. When a character returns from the demiplane, read: Nanna's cmpse twitches and grows, becoming bloated. It tears open with a wet ripping sound. Your ally bursts out of the corpse and falls to the ground, covered in black slime. Another entity emerges from the corpse as well - a headless woman, Blood sprays from the hole where he neck should be. She is hunched over, her arms crossed in front of her.
Blood Spray. All within 15 feet must make a DC 12 Dexterity save or be blinded by the spraying blood until an action is spent wiping the blood off of their eyes.
Flee. This is Nanna's new form, she's at full hit points and he has all of her spells available. She has blindsight 60 feet. She turns ethereal and flees.
The Hagborn. The character who emerged from Nanna's demiplane still has the arcane runes on their body. Baggy Nanna now considers this character to be her child and will in now way harm them. She might even show up to aid the character in some future adventure.