An Eruption Knife's blade is two-pronged and fans outward slightly. The blade is yellow-orange with black outer edges. The handle is shaped like one of the spikes on the Nobody logo and is silver.
"Eruption" is French, and like its English counterpart refers to the sudden release of pressure or energy, or a violent ejection of material, such as from a volcano.
Eruption's ground combo begins with two quick swipes, one going up and one going down, in turn. From here, the combo can be branched with a -Combo: immediately after the swipes, Larxene will jump in the air and throw her knives down upon the target. If a normal combo is continued, the combo repeats the two slashes, which also allows access to the same -Combo as before, and finishes with three low circular sweeps, knives brandished.
The aerial combo begins with one simple swipe upward, followed by a swipe down with both sets of knives. It finishes with a mid-air flip, arms wildly waving the two sets of knives about. A mid-air combo can be interrupted at all times, save for the finisher, with a -Combo move, in which Larxene tosses her knives down upon the target, identical to the -Combo available in the ground combo.