Luke - Backbiter

Now that his sword wasn’t swirling around, I could see something odd about it. The blade was two different types of metal-one edge bronze, the other steel.
Luke noticed me looking at it. “Oh, this? New toy. This is Backbiter.”
“Backbiter?”
Luke turned the blade in the light so it glinted wickedly. “One side is celestial bronze. The other is tempered steel. Works on mortals and immortals both.”
I thought about what Chiron had told me when I started my quest-that a hero should never harm mortals unless absolutely necessary.
“I didn’t know they could make weapons like that.”
“They probably can’t,” Luke agreed. “It’s one of a kind.”

***

The Lightning Thief, Chapter 22