Drill Sword

Jean (The Organization's previous Number 9) was the first one showing this Drill Sword. After the seven-year time skip, Helen, in memory of Jean, was shown to have mastered Jean's Drill sword, utilizing it effectively and because she has the ability to stretch her arms she uses it with no limitations.

Usage
The Drill Sword is a technique wherein the user twists its arm a number of times, then releases it, creating a drill effect. Jean is shown to be able to twist her arm up to 21 times, using up almost 50% of her Yoki. Helen, however, managed to reproduce this technique without expending any Yoki at all.

The Power of Drill Sword
Galatea describes Jean as performing "an attack with the most velocity and striking power out of all us Claymores." Her attack pierces Dauf's armor.

In Pieta, Helen immobilizes an insectoid Awaken Being's legs with her extendable arm, allowing Jean to sever the legs in a variant where the unwinding blade whirls like an airplane propeller.

The Drill Sword can drill through any Awakened Being or even hard rocks making it one of the strongest techniques ever.