Warhammer 40,000: Craftworld Eldar CYOA (Jumpchain-Compliant!)

From the introduction:

The Eldar. An ancient race, born some sixty million years ago in the War in Heaven. Raised from genetic stock cultivated by the Old Ones in their galaxy-spanning battle against the Necrontyr and the C'tan. Alongside the Krork, the Eldar were the foot-soldiers of the Old Ones, wielding the powers of the Realm of Souls against the soulless monsters they faced in the form of the Necron. When the Necron began their long sleep, the Eldar turned from servants to inheritors, bringing nearly the whole of the Milky Way under their reign – only to grow decadent and hedonistic as centuries became millennia became untold eons.