Gretkora's species were a humanoid species native to the Delta Quadrant. They had different various features like Humans, including some members having tanned skin and different body shapes, but all individuals had round green eyes, elongated hands with slender fingers, and brown hair.
They were a pre-warp civilization equivalent to that of Earths 21st century, although they had knowledge of faster-than-light speed. They managed only a quarter light-speed, but it had taken a ship three times larger than the USS Voyagers shuttle to house the engine. Scientists theorized the concept of warp-field coils and knew about antimatter converters. Before the visiting of the Voyager crew, they had not met members of other races before, and at least one individual serving in their military was worried about invasion by a more technologically advanced race.
They also appeared to have various types of medical knowledge, with at least one individual knowing about neural precursor cells. But laws did not allow to experiment with these cells, seeing the process as an abomination. Their religion taught that the body was pure and could not be defiled. Pursuing such a radical type of treatment would be considered a desecration, and experimentation could lead to being jailed or worse. Artificial and mechanical improvement was also looked down upon, and those that took that route to survive weren't allowed into their religious houses.
A sign of devotion included moving either one or both hands in a circle and ending with the palms held upward. Their God was called Kwolona, their Great Being. Their prophets told the story of Mannuse, a leader who lead his people out of their old home, which was in a valley surrounded by a deadly mountain range. It was told that Kwolona offered to give Mannuse wings that only he could use to escape, and could not save anyone else with them. So Mannuse refused the wings and led his people out one by one. This was where the basis of their religion came from, to not use artificial means to save oneself.
Seven of Nine and the Doctor crashed their shuttle on the species' planet. Paralyzed from her shoulders down, Seven was taken care of by Doctor Gretkora until the Voyager could come and rescue them. (VOY short story: "Choices")