Memento Iron Maiden

Memento Iron Maiden, also known as Embrace of the Merciful Saint, is the Sacred Gear wielded by Ichijou Tsukino in DxD: Twice Critical, substituing the original´s Boosted Gear. A mid-tier offensive-type Sacred Gear, it allows the user to instantly kills his target and store their 'shades', lingering parts of one's soul, to assistance in battle.

Summary
Despite its appearance and fame, Memento Iron Maiden was originally a Sacred Gear used to give solace and comfort for those 'who weren't ready to face death', giving terminally ill or dying ones a quick and painless death. Once their bodies were engulfed by the Iron Maiden, their shades were store inside a jewel on the user's hand and, on command, it could summon them to the living world as ethereal spirits, guiding them in accepting their deaths and come in terms with it until said spirit was ready to pass to the afterlife, being also able to take one spirit's appearance, memories and feelings in order to solace their respective loved ones.

Originally a support-type Sacred Gear, Memento Iron Maiden has been corrupted ever since the Devil Ichijou discovered its offensive potential regarding its power and abilities, ever since killing specific targets in order to absorb their appearance, identity, memories and even Sacred Gears. Since nobody dared to try to take him on in a fight considering all the knowledge and power himself have absorbed, him and his master Berolina Paimon were able to dominate Kuoh academy and the Gremory territory in it, also harassing and intimidating all the other supernatural creatures that weren't devils.

Appearance
Memento Iron Maiden takes the shape of a gigantic floating Iron Maiden torture device with a coffin-shaped form with several spikes spread all over its body and a saint-like form on top of it. In the middle, there is an entrance by two doors that reveals the spiky interior as well.

Memento Iron Maiden has also several chains tied to itself and linked to Ichijou's back in order to follow him by floating.

Abilities
Memento Iron Maiden has the ability to instantly kill those who the user touches under certain conditions. Once the target is caught and caged inside the Sacred Gear, his/her death is painless and intantaneous, leaving no body behind. Once the body is destroyed, their shades, a lingering part of their soul, is stored inside a jewel on the user's hand and with it, the user can summon the spirit in a physical form, which once destroyed will be stored yet again inside the jewel for later use. The user has total control other said shades, and it can even use the original abilities they had in life, including Sacred Gears, magical knowledge and inherited powers.

Moreover, the user can also change their appearance of the said shades, being able to retain and absorb their memories, feelings, knowledge and even use of their Sacred Gears, meaning Ichijou is able to use several other Sacred Gears as long as he keeps one's appearance long enough, also enabling him to take one's identity for spionage and information gathering. It's ultimate ability, however, is the ability of the user be able to escape death by changing places with a shade, destroying said shade in its place, being able to use this several times as long as there are shades left.

Due to it's size and shape, Memento Iron Maiden can also be used as a shield, being tall enough to protect both Berolina and Ichijou at the same time.

Conditions
In order to be used and be fully developed, Memento Iron Maiden must obey a certain number of conditions since it was originally a benelovent Sacred Gear with altruistic intentions. Even with its corruption, Ichijou must still follow said rules to fully grasp the sacred Gear's power and potential:
 * First and foremost, the target must fear death.
 * The target must be caught and be physically caged inside the Sacred Gear by Ichijou only. If this condition is not met or is met but the first one isn't, the Iron Maiden won't have any effect.
 * The target must believe or at least fear that Ichijou has any change of killing him or her, in other words, it must dread the user. This condition can be circled around by the user slowly destroying its target's pride, until they start to believe they're vulnerable and killable.
 * The user can only summon a couple of spirits for combat at a time, depending of its power and control over the Sacred Gear. Moreover, the user must use their own stock of stamina in order to summon and control one, otherwise the shade might become self-aware and be unable to follow its orders.
 * The user can only take one appearance at a time, meaning they are unable to use multiple Sacred Gears at once.

Weakeness
Memento Iron Maiden must strictly follow said set of rules, and if any of them are not met, no matter which, the Sacred Gear won't have any effect, leaving the user vulnerable. Moreover, the limitations one has over summoned shades are proportional to that one's stamina and concentration, and any interruption will cause the shade to be able to grasp self-awareness and even disobey the user's orders. Since the shades are still spirits, they are vulnerable to exorcism and other sealing techniques, which might lower the number of shades Ichijou can have at the time.

Balance Breaker: Purgatory Blaze
Purgatory Blaze(

), also known as the Light Goddess's Purification Flame, is the Balance Breaker for Memento Iron Maiden. Not much is known about it since Ichijou doesn't want to unleash it under unknown circunstances, but According to Elizabeth, this Balance Breaker allows Memento Iron Maiden to be a strong candidate for a Longinus.

Trivia

 * The images and appearance are based on the Wrath Shield from the Rise of the Shield Hero series.
 * The name of the Sacred Gear is a reference to Memento Mori, which means "remember you shall die".the medieval Latin Christian theory and practice of reflection on mortality, especially as a means of considering the vanity of earthly life and the transient nature of all earthly goods and pursuits.