Orbo is created from blood of the witches, that are captured by the STN-J. Orbo is used in a fight against witches in bullets and necklaces. It is created in a place called simply Factory, which is run by Takuma Zaizen. At the current moment only Seeds and those with the witch gene can handle to work with Orbo. Normal humans gain side-effects from being exposed to it. Though the factory is searching a way to find a way through that limitation and allow all the agents to use it in battle. As it grants a huge edge over witches. So because of that all the hunters of STN-J are Seeds or Craft users.
An air gun filled with Orbo that fires darts, which the hunters of STN-J use to stop witches. Shooting a witch with the darts renders them helpess and also dampens the craft once it enters a witch's bloodstream.
Orbo is also used in a necklace, placed in a vial that hangs from the wearer's neck. The vial of Orbo negates the effects of craft by absorbing the energy of it, making sure that no bodily harm will come to the wearer. But a skilled and focused user can bypass this and harm the wearer. It is possibly for a craft user to use a necklace like that, but it affects their craft too. Weakening them and possibly negating them as well while it is being worn.