Q: Though many Servants possess Noble Phantasms that appear in their actual myths and legends, there were some that felt like original creations for the game. What did you have in mind when you created these original Noble Phantasms (“Bounded Field of the Wind King: Invisible Air”, “All-Violating Talisman: Rule Breaker”)?

A: Invisible Air was simply a form of sorcery meant to conceal a Noble Phantasm. I thought that surely Merlin could have managed that somehow! Heroic Spirits that possess overly famous Noble Phantasms have a trick or two to hide their true identities.
[As for Rule Breaker,] I created it from her image as a treacherous archmage. I figured she would be too weak with only her Dragon’s Teeth soldiers.

Fate/complete material III; FAQ, pg. 134