Kalandan

A Kalandan Female

The Kalandans were an advanced space faring species of humanoids who built artificial planets for use as outposts in the 2nd millennium BC.

During the construction of one such planet,The Kalandan Outpost, the Kalandans accidentally created a deadly organism that infected and killed the outpost's inhabitants. Supply ships servicing the outpost inadvertently transported the disease back to the Kalandan homeworld, which presumably led to the extinction of their species. (TOS: "That Which Survives")