The Gadmeer, whose physiology is based on sulfur rather than carbon, were an advanced and peaceful race who fell victim to a superior military power. They placed their legacy, all their knowledge from 10,000 years of civilization, into an automatically piloted ship that was sent in search of a new homeworld to colonize. All that remained of the Gadmeer race itself was a multitude of biological samples. The completely automated ship was capable of communicating through a bio-mechanical representation named Lotan, and was programmed to terraform a planet by destroying all native organisms and replacing them with microbes that would create a new sulfur-based ecosystem from which the Gadmeer race could be reborn.
The enormous ship, two miles in diameter and capable of producing a curtain of energy stretching over twenty miles, had begun the terraforming process on P5S-381. Once begun, the terraforming had to be completed, but the process threatened to annihilate the newly settled Enkaran refugees on the planet, and two races were faced with the choice of extinction on a single world. SG-1's efforts favored the priority of the Enkarans, but their attempt to destroy the Gadmeer ship failed. However, negotiations with Lotan led to the discovery in the Gadmeer database of the original Enkaran homeworld to which the Enkarans were relocated before the terraforming process was completed.
Episode Reference: Scorched Earth