The N'shaii are a humanoid race native to the Milky Way galaxy. At least some members of the race were taller than the average Human, hairless and rather lean. N'shaii skin had the texture and color of parchment and facially, they had tiny black eyes, nostril slits for noses and a small gash for a mouth.
Culturally, the N'shaii were split into a number of different factions who had competed with each other for millennia. One of the N'shaii's favorite forms of competition was to see how many populated planets that one faction could hold. Their typical method of invasion was to place a number of autonomous satellites in orbit of the planet and bombard the major population centers below. Once the planet had been softened up, a mothership could move in and complete the invasion.
When the N'shaii first encountered the United Federation of Planets in 2257, during their attempt to invade Sordinia IV, N'shaii technology was more advanced than the Federation's, their weapons easily able to overcome a Federation starships deflector shields. However, the crew of the USS Constitution was able to overcome the N'shaii and their satellites, despite suffering heavy damage from a muon burst. Over the next eight years, the N'shaii encountered additional Federation starships as they attempted to conquer planets in Federation space. Following an encounter with the USS Defiant in orbit of Tenekratus IV, the N'shaii appeared to withdraw from Federation space and no further engagements were reported. (TOS - My Brother's Keeper novel: Constitution)