Knight Leader lightly shook his arm.
At some point, a longsword with a 3 cm wide blade had appeared in his hand. It was a sword with an 80 cm long blade that was optimal for knights to use on horseback. However, its silver surface was covered in something rough and dark-red.
[…]
The surface of Knight Leader’s dark-red longsword started to bubble.
The bubbling was not a mere chemical reaction caused by some chemical. Some of the bubbles were even about the size of a basketball. The tens and even hundreds of those large bubbles that were clearly wider than the sword itself appeared and altogether destroyed its silhouette.
The sword took on a new form.
It was now a gigantic sword over 3 meters long just like William’s Ascalon.

Toaru Majutsu no Index vol.18 ch.5 pt.3