When Arthur reached the gate and touched it, he realized that it was made of black metal, not stone.
He realized that the brown stony surface that he thought it had was only layers of dust that had settled on it over the years. So the circular stone gate was really a giant metal ring standing on its side.
He removed the layer of dust standing between him and the gate and touched the gate with the palm of his hand. Then he tried to input his internal energy into the gate.
There was resistance to his energy at first. But the resistance was quickly broken, and his violent internal energy made its way into the metal ring.
The metal ring absorbed his internal energy readily. Then runes on its surface lit up, and the whole structure hummed loudly like an internal combustion engine coming to life.
The loud hum was caused by the metal ring vibrating slightly. This vibration also caused the dust on the surface of the ring to shake loose.
