Marionette Heart

Marionette Heart (支配の心臓) is an Mental Magic used by the former Demon Lord Clayman. It was one of the best-kept secrets of Clayman's mystical powers.

Abilities
Marionette Heart is one of the most secret techniques used by Clayman to carve cursed seals directly on subordinates' biological hearts. After the seal was engraved, the real heart of the recipient would be replaced by a magical device, turning them into personal eternal marionettes carrying out his bidding and unable to go against the will of their master. Fabulously expensive magical media alongside the magicules of the target would turn the receiver into a Majin, continuing their lifespan and augmenting their power. It is one of the few possible solutions to change an evolutional path. While the temporary heart would be placed into a person's body, the biological heart would be kept in a special container to sustain it and continue to beat. Additionally, the pseudo-heart could be used for information-gathering purposes as a wiretap. Through Marionette Heart it is possible to listen and communicate between the host of the magical gadget and the keeper of the real heart. The form of encrypted communication used in Marionette Heart runs on electric signals and natural geomagnetism similarly to Clayman's Unique Skill Manipulator, without the use of any magicules. A temporary heart also emits encrypted signals that run across the ley lines and return to the master without being noticed by the host of a heart. Marionette Heart also can be used as an effective blackmail instrument. The organic heart kept in the container can be hurt and all damage done to it would also transfer to a magical device. Destroying a biological heart would kill its owner. On the other hand, if the pseudo-heart would be demolished, the real one would crumble into ashes and disappear.

Trivia

 * If the biological heart is returned properly to its receiver, it will successfully merge with Majin's body and will continue to function as usual. If Marionette Heart's magical replacement device is removed without implanting a new heart substitution, the host would perish due to reverting back into its Human form and with an absence of Marionette Heart to continue the lifespan.
 * In Slime Diaries spin-off, Mjurran's heart would become a running joke. Often, in order to encourage and motivate Mjurran to complete Clayman's missions and bidding, he would threaten to squeeze her organic heart as strawberry jam. We can also watch as the container containing her heart would be used as a balancing toy, like a brittle vase, showing that at the time Clayman, due to Tatsuya Kondou's brainwashing, did not care about his subordinates and Mjuran's heart became merely a fragile decorative element and attribute of the Clayman Cabinet. Later, when Mjurran tries to question his master's orders and showed some form of resentment, her punishment became even harsher and crueler. If she failed, her heart would be used as filling for a special pie prepared personally by Clayman and fed to the Nine-Tailed Beast. Eventually, when the heart turned to ashes, Clayman baked this "heartwarming" cake after all.
 * Still, when Marionette Heart was sending Clayman the encrypted signals through ley lines, he was forcing Mjurran to file detailed reports with him anyway as a precautionary measure to make sure she never noticed him being aware of everything that happened with her.
 * While Clayman used Marionette Heart to transform people into his puppets, Mokshan was able to use the curse to increase his own power itself. It should be noted that while the curse operates the same way in both the Central World and the Mirror World, both have different mechanics due to the laws of the respective worlds they are used in.

Gallery

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