Marionette Dance

Marionette Dance (踊る人形達) is an Art used by the former Demon Lord Kleiman.

Abilities
To begin with, this technique requires the user to magically create golems. The golems are wood-like in appearance, looking like art mannequins or marionette dolls with a large jewel embedded into their forehead. The user then traps the soul of a Majin and implants it inside of one of these miniature golems — most likely within the jewel on their forehead — before storing the golem away inside of spatial storage, thus completing the preparations.

Once these preparations are met, the user is free to summon the golem/s from within their spatial storage at any given time and activate the dormant golems. Once activated, the small marionette/s grow many times in size and take on the appearance of the Majin used in it's creation. The golem bears all of the abilities and power of the original Majin, and due to their nature as golems made of magic, as long as their spiritual body is intact they can regenerate from any damage. From here the user is free to manipulate the golems in any way they wish, manipulating the equivalent of an army as if it were an extension of their body.

Trivia

 * In That Time I Got Reincarnated as a Slime: Isekai Memories, the "Kleiman [The Marionette Master]" unit uses this as a Secret Skill.
 * Rimuru noted that despite the Art's practical usefulness, the dolls were poorly made, stating that they didn't have any defensive spells to them that would protect them from spiritual attacks, implying that the Art was either incomplete or Kleiman never bothered to apply defensive spells to them. This poor craftsmanship is presumably attributed to his forceful brainwashing,
 * In the Manga, when Kleiman uses Marionette Dance, each doll takes the appearance of various Majin, each different from one another. In the Anime however, all dolls simultaneously take the appearance of the same Majin instead.