The wind had come from Saber's sword. ... More specifically, that was Invisible Air's doing.

The bounded field of condensed pressure that could refract light had leaked out in just an instant. The instant it had clashed with Lancer's spear— the prana controlling the wind around the sword had become loose.

And at that moment, Lancer had caught a glimpse of the shape of the "true sword" inside the torn bounded field. Lancer's murmur from before was the proof that it was definitely his spear that had exposed Invisible Air.

- Fate/Zero: Act 3, Part 5