Jeanne's Iron Maiden

The Iron Maiden (アイアンメイデン, "Aian Meiden") is a torture device used by Iron Maiden Jeanne.

About
The Iron Maiden is made of iron and is quite heavy to push. There are so many spikes and nails within it that even someone as thin as Jeanne gets hurt. While she is within it, Jeanne heals herself while she is being hurt so her Furyoku rises gradually. She remains within it during most of the Shaman Tournament where she also uses Cargo Ship X´s crane to subject herself to water torture.

Jeanne uses the entire Iron Maiden as a medium for her main Over Soul with Shamash and after her son, Tao Men, inherited Shamash, he would use a single spike from the Iron Maiden for his own Over Soul.

Marco Lasso protects the key to the Iron Maiden and keeps it within his shoulder pad. Despite needing a key, Jeanne is somehow able to open the Iron Maiden from within, without it.

During the fight at Mū, the Patch Priest Magna crushes the Iron Maiden in an attempt to take out Jeanne, but she was not within as she had stayed behind after exhausting her Furyoku during the previous fights. After the tournament, the Iron Maiden was restored and put in storage at the Funbari Onsen where Umemiya Ryunosuke would polish it every day. At some point the Iron Maiden was replaced with a replica by an unknown person. The face mask of the original was given to the Black Maiden to be used as a medium for the Over Soul she created with the spirit of Jeanne herself.

Anime/Manga Difference
In both the Japanese and the English version of the anime series, instead of spikes, the Iron Maiden contains thorny vines that are wrapped around Jeanne.

The anime series also change the backstory of Shamash and the Iron Maiden, explaining that when Jeanne prayed to him, Shamash gave Jeanne her powers in exchange for her entering the Iron Maiden.