The Lives of the Thousand Gods are an item that appears in Ninja Gaiden (Xbox), Ninja Gaiden Black, Ninja Gaiden Sigma, Ninja Gaiden Sigma Plus, Ninja Gaiden II, Ninja Gaiden Sigma 2, and Ninja Gaiden Sigma 2 Plus.
Quoted directly from the game: "A strand of nine Life of the Gods jewels. Just one of these is enough to immediately increase the limits of one’s physical endurance. Its exaggerated name comes from this immediate effectiveness. Because Life of the Gods jewels are difficult to come by, receiving nine at once seems to increase its value a thousandfold. It is suggested that this item originated with someone who realized the power of Life of the Gods jewels and decided to string them together. Many were made in Japan during the 15th century, but since then, they have travelled to other countries through trade. Most were exported as decorative items, and records show they were often traded for a large number of silver pieces"
Collect and use Lives of a Thousand Gods to permanently increase Ryu Hayabusa's health bar, and it is wise to save them for a difficult boss as it fully restores Ryu's health bar also. As the name implies, it is a thousand times better due to the effects, easier to purchase as they cost 7000 essence while it takes 9000 to buy 9 Lives of the Gods.