Night on Bald Mountain/Ave Maria is the final segment of Fantasia, following the music of the same name by Modest Moussorgsky and Franz Schubert. Deems Taylor introduces it as the conflict between the profane (represented by Night on Bald Mountain) and the sacred (represented by Ave Maria).
At Walpurgis Night (the Witches' Sabbath), Chernabog, god of evil, emerges from the peak of Bald Mountain (in reality Mount Triglaf, near Kiev in southern Russia) to summon all of his minions, including ghosts, demons, hags, and harpies, who dance furiously as he throws them into the mountain’s fiery pit. Chernabog is driven away by the light of the dawn, and a procession of figures walks up a hill to witness a sunrise. It is perhaps the most famous sequences in Fantasia, if not, second to The Sorcerer's Apprentice. The sequence showcases the animation of Vladimir Tytla and the style of Kay Nielsen, as well as the longest shot ever produced in the multi-plane camera (in the procession).
The sequence takes place in a mountainous area, in which a village is overlooked by Bald Mountain. The peak of Bald Mountain is revealed to be Chernabog's wings, which he spreads out as he looks at the village down below. Stretching out his arms, Chernabog casts a dark shadow over the village and summons ghosts, including the spirits of hanged criminals (who pass through the noose a second time as they rise from their graves), fallen warriors in the moat and grounds of a ruined castle and the souls of all who are not buried in sacred ground.
The ghosts join together to become a single mass, swirling around Chernabog, who laughs and summons fire and demons. As the demons emerge and gather below their master, he grabs a number of them and disdainfully throws them into the fires of Bald Mountain, while his other minions dance on. He then uses flames to create images: first, the flames resemble elegant dancers; then, at his pleasure, they transform into dancing barnyard animals. Chernabog then transforms them into blue demons, who dance before him, causing him to grin maliciously. As the dancing continues, it becomes more frantic and chaotic; Harpies fly above the demons, occasionally grabbing them and throwing them into the inferno.
The celebration culminates in a blinding flash of fire from the inferno. Chernabog, ready to continue, eagerly leers over his minions but is interrupted by the sound of bells, which herald the coming of the dawn. Though he initially ignores the sound, the light of the sun forces him and his minions to retreat; as the ghosts return to their resting places and the demons hide in the mountain, Chernabog raises his arms one final time and closes his wings, protecting himself from the sunlight and becoming the peak of the mountain once more.
A long line of figures (possibly nuns), each bearing a source of golden light, gradually comes into view in the land in front of the village. The silhouettes proceed up a shallow-sloping hill, among natural forms that resemble the architecture of a cathedral (trees are tall and completely vertical, resembling columns, and branches cross together to form gothic arches), the predawn sky filled with color by the coming sunrise. The camera continues ahead of these figures and reaches a serene horizon, where the sun slowly rises to a crescendo. The film then ends immediately, without any disclaimer.
The idea for Night on Bald Mountain's Devil was conceived by German artist Heinrich Kley (who, though he did not work at the Disney studio, inspired many of the Disney artists, and whose drawings were collected by Walt Disney), who once sketched a pen and ink drawing of a gigantic demon forcing workers out of a factory by blocking the chimney. Albert Hurter, inspired by this drawing and others like it by Kley, drew various sketches of a huge, winged devil tossing handfuls of souls into a volcano. Hurter's sketches also included studies of Chernabog's hands as his flailing minions attempt to clamber onto his fingers for safety; this imagery is used in a shot in the final film. After Hurter's initial sketches, Kay Nielsen established the final appearance of Chernabog and his world in a series of detailed pastel illustrations, as well as a model sheet for the character. Chernabog was then created as a real model, to be used as reference by Tytla during animation.