The Seventh Spellblade

"Arise". Nanao gets behind rogue upperclassman Vera Miligan and charges to attack, only for "Snake-Eye" to reveal she has an ace in the hole: a second basilisk eye embedded in the palm of her left hand. With no other option, Nanao wills her blade to strike faster than the light from the eye itself, cutting space and time itself to sever Miligan's hand before the attack can reach her (shown as the camera lens cracking). Oliver explains in a voiceover that, in the lore of the series, such an unblockable strike, executed within the "one step, one spell" distance, is known as a "spellblade" -- and furthermore, this one is entirely unknown to the world of magic. Like many of her other strange abilities, Nanao herself has no clear idea how she did it and is unable to subsequently reproduce the feat.

Example of:
Unblockable Attack