Madou Necklace Silva (魔導具シルヴァ, Madōgu Shiruva?) is the Madou Necklace of Zero. She belonged to the former Silver Fang (Rei's father) and serves the current one. She takes the form of a Madou necklace of a woman wearing a mask. It was Silva that identified the killer of Zero's family was related to another Makai Knight. It's unclear of Silva's true potential since Zero never once used his blades or techniques with Silva as Kouga does with Zaruba. For now she's merely an advisor and Horror detector.
In Garo Special: Beast of the Midnight Sun, Silva is no longer a necklace. Her head has been pinned to Rei's glove. Towards the end of Beast of the White Knight she suggested Rei to take Akatsuki as his student, but Rei said Silva's company is enough.