The Magic Stone

The Magic Stone is a most powerful object in the center of a Stonehenge.

Description
The stone is in a 7 pointed shape, it has many circular, triangular patterns at the bottom, Three blue glowing rings in the middle of the stone on both sides, On the base of the stone are many stones surrounding the stone.

Role in the film
The stone has a magical sword, Excalibur sticking out. The rings can glow that the rightful heir is near the stone, Arthur pulls Excalibur out and became king.

The rings still glow forever as Arthur remains king. Later after Excalibur was stolen it had thorn like vines growing on it and the rings' glow disappearing. Later when Ruber mistakenly stabs Excalibur back into the stone, the vines breaks off as the stone's rings to glow and its power conflicts with the ACME potion (that Ruber used earlier to fuse Excalibur to his arm earlier and making his iron henchmen three days earlier) which sends a powerful wave that reverts Ruber's henchmen including Bladebeak back to their normal selves. Ruber is then disintegrated by the stone which then restores Excalibur. After the stone's power fades away, One of Ruber's shoulder pad (what's left of him) lands next to the stone.