Blackbird Clan Lord Leona Blackbird:
It's the Giants' technology and its natural ability; the root of power that made it possible for the Giant to challenge god as an equal.
It'd be impossible to steal from Helios at his full strength but since he is on the verge of ruin, I'm sure you could steal the Origin of Giants from him. Please go to the Fallen Emperor's Throne, defeat Helios and bring the Origin of Giants.
Hierarch Kekropus from the Town of Giran will know exact location. He is expecting you, so please go talk to him.