Echoes spill out from the titanic mushroom, a cacophony of wheezing voices that wrap together like some kind of discordant music. Though you dread it, you're drawn inside by the horrible song. The palace is hollowed out, with spiraling stairs and balconies carved into its walls. The interior is lit by phosphorescent patches of mold growing in whorls.
Moving up and down the stairs is a parade of creatures, their bodies only vaguely humanoid, with clusters of tumescent growths forming chaotic patterns on their decaying flesh. In the center of the open space floats Zuggtmoy herself, womanlike in form, but made entirely of fungi and mold. She is easily three times the height of the bridesmaids currently tending to her. She appears to be deep in meditation as her subjects croon a strange, soothing song. They weave the substance of her giant figure into delicate lichen veils and a long, mycelium train like a bridal gown. Their voices stab into your minds, both insane and gleeful in equal parts.
A vision invades your mind, temporarily blocking your view, and you're filled with paralyzed terror as you realize you can't escape it. Your bodies are vulnerable, face to face with a Demon Lord, and you can do nothing but watch the scene that plays out in front of you. Myconids and fungal creatures throughout the Underdark have fallen under the influence of her spreading spores, making a slow and steady march around the Darklake. Thousands are on the move, and the procession has a bizarrely festive air. At their destination, 12 bridesmaids and 6 chamberlains make preparations for a sick mockery of a wedding ceremony. Two of them are carrying the grotesque corpse of Yestabrod, puppeting it to rehearse its role as priest. The demonic song that has plagued Sarith for months echoes in your own minds:
From Shedaklah, her palace grows
From chaos dark, her love She shows
Yearn! Dance! Laugh!
Soon, the Lady will be wed
Her joyous spores will be spread
Hunger! Devour!
Youth is gone and beauty rots
Zuggtmoy, Araumycos
The Bride! The Groom!
Joined together, heart to heart
Becoming one 'til death do part
Hail! Hail! Hail!
The song ends and you're whipped back into the present. Zuggtmoy's eyes have opened and she stares into your souls. Everyone, make a wisdom saving throw.