Echo didn't seem to have any individuality to set her apart from an empty doll, however as time passed Echo has proved this initial impression wrong, making it apparent that she simply has difficulty expressing herself.

History

She is Vincent Nightray’s servant who boasts high combat skills. Since her calm, level-headedness allows her to accurately assess a situation, she can perform high level missions such as scout outs and intelligence activities. Her acquaintance Gil also acknowledges her extraordinary skill. Before she simply did nothing but follow her master’s orders and from that image she came to call herself a “puppet.”

Echo is also the spilt personality of the Baskerville named Noise (Zwei) who adores Vincent and manipulates the Chain Duldee, who raided Oz’s Coming-of-Age ceremony. Echo’s original name is actually Duldum, with Echo being a name that was given to her by Noise, and her main purpose is to act as Duldee’s puppet and to help prevent Noise’s sanity from collapsing. Since she elapses arbitrary into unstable emotions, through Vincent’s orders, Echo has shut out Noise’s personality.

Due to both her and Noise’s presence within the same body, the majority of the Baskerville Clan has taken to calling them 'Zwei', meaning “Two”, to act as a play on Echo’s dual personalities.

Abilities & Powers

Possession: As a split personality created by Duldee, Echo had the ability to take the place of Noise as the active personality. However, due to Noise's adopted aggression, Echo tended to only take on her role as the active personality whenever Noise was ordered by Vincent to recede into her subconsciousness.

Maintenance of Heart: Like her predecessors, Echo was capable of picking up the broken pieces of Noise's heart and absorbing them in order to keep them safe until the day that Noise could reclaim them herself - as was her duty as Duldum.

Hand-To-Hand Combat: Echo was a skilled combatant, often making use of a unique acrobatic technique whilst sparring against opponents with her twin blue-bladed short swords. However, in battle Echo tended to focus moreso on the exact orders she'd been given, and would even on occasion be compelled to take action in certain situations without consciously being aware of why she'd done so.

Hyper Endurance: All Baskervilles possess enhanced speed, strength and endurance as an effect of being chosen to act as messengers of the Abyss. Thus, due to her connection with Noise, Echo possessed such qualities as well - allowing her to carry on in battle without tiring and endure against extreme conditions that regular humans would have difficulty coping against.

Healing: As a Baskerville, Noise was able to heal from her wounds at a rapid pace - even moreso than her older colleagues because of her young age. As such, Echo could also heal her wounds - only when serious wounds were inflicted on either personality, Vincent would have them switch so that either Echo or Noise could heal fully without interruption while their counterpart continued to do his bidding.

(Taken from Guidebook 18.5: Evidence & Echo's Wiki Page)