The Malachi Configuration was intended to be used as a prison for Greater Demons.
It is created by driving the seraph blades that are part of the Configuration into the ground at the four cardinal points around the being to be contained. Bright light will shoot out from the four blades and will form the walls—surrounding the being—of the cage; the walls are seemingly made of shimmering, moving filaments of light, though only the blades and the bottom part of the walls ordinarily remain visible after it is activated unless it is disturbed.
Despite its intended purpose, the original Configuration is not powerful enough to hold against the Greater Demon Lilith. Isabelle Lightwood made upgrades to the Configuration, which proved powerful enough to hold Lilith. She also added a feature where twisting one of the seraph blades forming the cage wold inflict pain on the prisoner.
In 2016, Isabelle Lightwood, as the New York Institute's weapons master, read about it and told her comrades about it when they were discussing a way to contain the brainwashed Jace. With help from Imogen Herondale, then Inquisitor who was able to grant them access to the Armory, Isabelle was able to sneak the cage out in a duffel bag after disassembling it. Isabelle, Alec, and Clary later reassembled the cage and trapped Jace inside.
Some weeks after, a Malachi Configuration, upgraded by Isabelle, was used to hold Lilith, who was summoned right in the middle of it. When Lilith refused to cooperate, Isabelle and later Jace twisted one of the seraph blades to torture Lilith into talking. Cain later removed one of the seraph blades to allow Lilith to escape.