Serpentine creatures employed by the Devidians to open temporal rifts, allowing them to travel to nineteenth-century Earth and steal human neural energy in Time's Arrow.
The ophidian appears in the two-part Next Generation story Time's Arrow. It is a snake-like creature that, when stimulated, can focus energy to tear an opening between one time and another. The Devidians, who live slightly out of phase with normal matter on Devidia II, depend on it for their journeys into the past.
In San Francisco in 1893 two Devidians pose as a well-dressed human couple. One carries a cane with an ophidian for its handle, and under cover of a cholera epidemic they drain the neural energy of the dying and carry it home through the rift.
Data, thrown back in time, recognises what the cane is and snatches it. The struggle over the creature in a cavern beneath the city scatters Picard's party across two centuries, and the Enterprise finally destroys the Devidian site with modified torpedoes.