True to its name, an Irrégulier Knife has an oblong shape, somewhat similar to Xemnas's Fury Ethereal Blades. It has an "S" shape with a small, red handle. The rest of the blade is black with gold edges.
Irrégulier is French for "Irregular".
The Irrégulier's ground combo begins with two quick swipes, one going up and one going down, in turn. Continuing the combo results a repeat of the former move, only adding a -Combo in which Larxene jumps in the air and slams down upon the ground, Knives first. The combo finishes with a low, circular sweep, Knives brandished.
The Irrégulier's aerial combo begins with a simple swipe to the left, and it is followed by a flip in the air, swinging both sets of Knives outward and down. The combo finishes with a Knives-first downward slam upon the ground.