The Ritual of Infernal Conversion involves seething the Sword until it's red-hot and cooling it four times, each time in the blood of a slain Downworlder child: once in the blood of a warlock child, once in the blood of a werewolf child, once in the blood of a fey child, and once in the blood of a young vampire. For the purposes of the old spell, the child for the sacrifice would be any Downworlder under the age of eighteen. The amount of blood needed for the ritual is enough to drain the being of blood and effectively kill them.
When the Sword's angelic alignment is reversed, it will become demonic and dark in nature, with a power that is equal to the angelic power it once possessed.
When the ritual is performed on the sword, the sword will allow the user to control demons, allowing him/her to summon even hordes of and compel them into obedience. Even a partially complete ritual will have enough effect on the sword to grant the wielder some power over demons.
In September 2007, the Shadowhunter Valentine Morgenstern began to make preparations to accomplish the ritual. He began by having the warlock Elias summon the Greater Demon Agramon and had the warlock killed—making Elias—a child warlock—the first sacrifice for the ritual. Valentine then used Agramon and his power to help him gather everything else necessary for the ritual. Agramon was able to overcome the Silent Brothers as Valentine stole the Sword from the Silent City.
Valentine continued to use Agramon to scare some of his targets to death, including a young werewolf, Joseph. This attempt failed because they were interrupted by Bat before he could get enough blood from the cub. Shortly after, Valentine was able to drain the blood of a faerie child in Central Park.
To complete his ingredients, Valentine abducted the werewolf Maia Roberts and the vampire Simon Lewis. Maia was rescued in time, but Valentine was able to drain Simon's blood—the latter survived, however, because Simon was a vampire and Jace got to him soon enough to give his blood and save him.
Valentine was able to perform the ritual after successfully draining a werewolf child of blood on the outskirts of the Brocelind Forest, completing the necessary blood requirements. Valentine was then able to use the Sword to summon and control hordes of demons to wage war on the citizens of Alicante.
- The ability to turn the Sword dark is not typically known to many, but the information on the ritual can be found in a warlock book—a big book bound in a green cloth, written in Purgatic, which Magnus Bane has a copy of.