Inferring from the position of the hand bones valley, then the place where the white gate of bone was located was probably the Giant's head.
This was a huge irregular spherical space, the ground was filled with mud while a small mass of flickering flame stood in the center of the sphere, illuminating the surroundings.
The small mass of flame appeared to be incredibly weak, but was giving off an extraordinary sense of warmth to everyone present. Looking at the flame, one would feel like it contained everything in this world.
This was the first flame, that which created all things in this world. Despite looking like an ordinary flame, it was in fact the manifestation of this world's authority, from which the authorities of the three Gods originated from.
And now, Nala who had the power of the three Gods would need to turn herself into a Torch and fuel this flame, once again purifying the world of the Black Abyss.