A pre-industrial reptilian species of the desert world Persephone III, who faced extinction in 2259 when a comet was found to be on course to strike their planet.
The Deleb are humanoids with purple scaled skin, heavy cranial ridges and yellow eyes. Federation surveys counted several million of them on arid Persephone III, living at a pre-industrial level. They appear in the Strange New Worlds episode Children of the Comet.
The USS Enterprise sets out to push the comet off course, only to find it shielded and guarded by the Shepherds, zealots who revere it as a sacred arbiter of life and forbid any interference. Cadet Uhura deciphers the musical language of a structure inside the comet while Pike spars with the Shepherds.
Spock uses a shuttle's shields to heat the comet's surface, and it shifts to a safe path. As it passes, vapour from the comet enters the atmosphere and brings rain, a change that Spock expects to help Deleb farming and society.