Saiya-jins are legendary fighters who show no mercy. They're feared across the galaxy because of their power and their heartlessness. They come from the planet Vegita which is destroyed by Frieza, only a few Saiya-jins survive among them Goku and Vegita. The Saiya-jins have many different forms in which their power level is stronger or weaker. Learn more about this in Saiyan Forms. Saiya-jins are born with tails which give them the power to turn into a giant ape-like creature. When this tail is cut off they no longer have that power. Also, if a Saiya-jin is near-death, when he recovers he will have plenty more strength than he did before.