Surtr was a secondary class pallasites. He is not a human. As a pallasite, his time control and another powers, depends of his weapon (stone) and with out it, the distortions made by him disappears.
Life and Death
Surtr is sent to kill and understand Shun, Kouga, Souma and Yuna. He makes a barrier with the cosmo of the Stone that Pallas gived to him, and repels the attacks of the saints. Only with Shun help, the quartet defeats Surtr.