 However, the majority of Firvulag have only weak mental powers, whereas the Tanu wear torcs, which are also mind-amplifying devices to allow use of their mental powers.The Tanu are generally much longer lived than the Firvulag.The four books of the Saga of Pliocene Exile abound with Tanu who are more than a thousand years old, who were not born on Earth, and who are called 'first comers' because of the fact.