Utilizing the energy converted from sacrist fragments, the Faust Robe is a protector created through alchemy techniques. From this description, one may say it is an object that is incredibly similar to the Symphogear. However, there is a significant difference. A song (chant) is not necessary to activate it. In Carol’s case it normally took the form of a harp, the same as one talked of in legend, however when she plucked the strings the harp changed form and adorned to her body. The sound produced by the strings not only amplified Carol’s alchemic powers, but also proved incredibly flexible and useful in battle. A swing of the strings created an intense slashing attack capable of bisecting objects, and demonstrated various capabilities in battle by changing its form. It exhibited a combat potential that did not lose out even when faced against multiple adaptors.
However, this power carries a heavy price, as she is forced to burn away her memories in order to use it.
While it initially seemed like it could be overpowered by the Ignite Module, it was later revealed that Carol had been deliberately holding back and allowed herself to lose. In her second battle against Hibiki, Tsubasa, and Chris, she came dangerously close to defeating them, even though they used the second and third phases of the Ignite Module's power.
When activating, the user can't choose the amount of memories they want to burn, however, it's known, once activated, the user can burn as much memories as they like. This is widely shown in GX on Episode 13, when Carol burned most of her memories, turning her strings into a dragon-like monster. This was also the main cause of her amnesia.