A nebula where a spontaneously formed intelligence trapped the Enterprise in 2259 and recast its crew as characters from a storybook to please M'Benga's daughter.
The Jonisian Nebula is surveyed by the USS Enterprise in the Strange New Worlds episode The Elysian Kingdom. When the ship tries to leave it is held fast, and Dr M'Benga wakes to find the crew dressed and behaving as figures from The Kingdom of Elysian, the book he reads to his daughter Rukiya, with himself as King Ridley.
Only M'Benga and Hemmer, whose Aenar telepathy protects him, keep their memories. They trace the transformation to an intelligence that arose by chance within the nebula, a kind of Boltzmann brain, which sensed Rukiya's loneliness in the transporter buffer where her father keeps her to hold off a fatal illness.
The entity cannot cure her outside the nebula but offers to let her live on with it, free of her body. M'Benga agrees to let her go, and she briefly returns as an adult to tell him she is happy.