Forged of timeless power yielding
Strength only to Arthur, see
Excalibur in stone and water
Wielding flames while Avalon remains
Above the elements, for healing.
I'm not sure how well it fits the Challenge but I tried:
Write in any form you desire about who, when and why Excalibur was forged and what happened to it after King Arthur gave it back to the Lady of the Lake.