Sarastra's Prison

150 years ago, Sarasta, also known as Auril, Queen of Night and Magic, was tricked by members of the Seelie court and was trapped on the material plane. She has resided in her prison within the village known as Ezra's Field since then. Some lesser members of her court, 3 night hags, have found her prison and been trying to help her escape to curry favor for the past 50 years.

Main Chamber
The prison lies within a well in the center of the village. After descending 35 feet, there is a main circular chamber 50 feet in diameter. This room is covered in snow and Winter Tulips. The walls are stone and have intricate carvings and text all along them.

Within the room are 2 Ice Maidens with their Ice Drake pets. These fey creatures were the first to find the prison, but were trapped along with their Queen. Corrupted by Seelie magic, now they only wish to have companions to stay with them in the cold. They will approach any humanoids that enter the well, enticing them to stay. They will approach males first, and will try to kiss them. If the recipient of the kiss is willing, they have the following happen: If they are unwilling, they may make a Strength or Charisma saving throw against the Ice Maiden's spell DC. On a failure, the above effects still happen, but they may repeat their Charisma saving throw at the end of each of their turns. On a success, they resist the charm, and are immune to its effects for the next 24 hours.
 * They are charmed by the Ice Maiden to stay in the snow, and to protect the maiden at all cost.
 * They gain immunity to cold damage, and vulnerability to fire.
 * These effects can only be removed by a Greater Restoration spell or similar effect.

The 6 Realms
The door to the Prison room itself is well protected by a puzzle. There are 4 doors that lead out from the main chamber, each of which is approximately 35 feet long. The only distinguishing characteristic about the hallway is that there is an image of an oak tree, with a black gemstone in the middle, on the left side. Going through the hallway will seem to deposit the players in the same room they left. However, the nature of the chamber is a folded dimensional space. The players will reside in the same area, and be able to interact with eachother as normal no matter which hallway they enter. However, the room they're individually in is different, and is represented by the inscriptions on the wall.

There are 6 unique rooms, and each are connected like the faces of a cube. Each room has an inscription that says in Sylvan

"Place the charm between the Moon and the Snow"

In addition, each room has additional inscriptions and carvings that describe the nature of the realm.

1 The Lord of the Hunt
''Astride a midnight horse sits a shirtless elven huntsman. His broad chest is thickly muscled and sports tattooed knot work. Great stag antlers crest the huntsman’s head, curving above his rich brown hair. A massive spear twined with glowing green vines drives forward in his clenched fist.''

"The baying of shadow hounds; thundering hoof beats; a brassy horn note; the Wild Hunt is coming, and pity its quarry"

2 Bear King
''Dressed in hunting leathers with a thick bearskin cloak around his shoulders, a bearded king sits upon a throne carved from a whole tree trunk. A crown of holly leaves wreathes his head, and a blackened maul rests near his hand. An ornate clay pot filled with honey hangs at his hip at all times.''

" 'Old Honey Paws' rules the northern kingdom of Bjeornheim. His realm is full of merriment and sport, and his love of sweets is only rivaled by his love of challenge. All are allowed to challenge him for his throne at any time, but none have succeeded."

3 Moonlit King
''Dressed in archaic nobleman’s finery, this elf lord has wildly unkempt hair and pale, almost luminous skin. His eyes bulge slightly from their sockets as they stare vacantly.''

"Consumed by madness, the Moonlit King is an ephemeral vestige of greatness lost. Exiled by his lover for some transgression long past, he is beset by phantoms from his own mind conjured from shadows and regret."

4 Queen of Witches
''This statuesque woman towers over any tall man, and most ogres. Her hair falls in a cascade of curls and looks as if it is spun from copper. Her eyes have no iris or pupil. A billowy robe of forest green enshrouds her body, and she grasps a great ring of etched silver in one massive fist.''

"Keeper of pacts, granter of power, the Queen of Witches is sought after by all the ambitious. Attended by witches, hags, and mortal supplicants, a single hair from her head is more power than any mortal should ever desire."

5 River King
''This powerfully-muscled elf lord wears a foam-trimmed cloak and a vest of woven reeds and willow branches. His crown shines like the sun on a lake, and his flowing hair curls and moves even when there is no wind. An orb of light that ripples like water circles his hand.''

"Just beyond the river's reflection, you will find the realm of the River King. Stern but caring, the King has a great love for his people. Beware pacts made with him, for the river may change its course when it wills."

6 Snow Queen
''This severe elf's gown is exquisite, fashioned of luminous blue fabric that catches light and shines from within. Lacy ice crystals accent the gown, and a snow-white mantle cascades from her shoulders. Icicles radiate in a crown-like halo behind her head, drifting gracefully through the air.''

"The cold-hearted Snow Queen, Daughter of Boreas, rules a northern kingdom in the Frozen Reach. Shrouded in snow and ice, the realm reflects the nature of its mistress: inhospitable."

Solution
After deciphering the messages and understanding the nature of the Chamber, the players must find the pathway that connects the Snow Queen and Midnight King's realms. Once there, they need to cast a charm sell on the black gem within the Oak tree. The Tree will open into a starry portal. Walking through the portal will deposit the players into the next room.

The Cell Door
If there's enough time left in the session (approximately 1.5 hours or more), there will be a combat encounter here - 3 Ice Elementals.

"Before you are large doors, 15 feet tall and made completely out of cold iron. It is decorated in a dwarven style, but has Sylvan text in three lines on it."

The text cannot be read by Auril, or any other fey creature, due to it being written on cold iron. When deciphered, they say: "Touch of a devil; Kiss of a devil; Tongue of a devil". In order to open it, the door must be touched by a fiend, while touched by fire, while spoken to in Infernal.

The Prison
''"Wha-...where am I? Who are you? Where's mommy and daddy?" - Odessa.''

Once the door is open, the main Prison is revealed. Inside is a room covered in shadow. On a bed of snow and winter tulips in the center of the room is a sleeping fey woman, of stunning beauty with hair the color of midnight. A gown seemingly woven from the night sky drapes her flawless ivory skin. Bright lights glitter like diamonds in her crown and raiment, and some drift about her body and dance near her hands. She glows like the moon and the shadows throughout the room seem to dance on the walls.

The Queen of Night and Magic, reunited with her body, her prison opened, will leave Odessa's body and return to her own. Her eyes will open, and she will sit up. There will be a brief demonstration of her power to put fear and awe into the hearts of the adventurers, then she will offer them a single boon - A single question that she will answer.