Magic Sealing Stones (魔封石 Mafū Seki) is a Magic Item used to imprison Mages.
In the manga, true to its name, Magic Sealing Stones are used to construct prison cells out of Magic stones; utilized to incarcerate Mages: rendering their Magic abilities ineffective when inside (e.g. Cobra's Sound Magic), including noteworthy Mages of preeminent Magic Power such as former Magic Councilor Jellal Fernandes and the Dark Guild Oración Seis. However, Mages are able to inflict damage upon imprisoned prisoners from the outside, displayed when Nadal heavily tortures Jellal Fernandes with a Magic beam from his Magic Staff. This has been proven further when Doranbolt uses his Teleportation Magic to rapidly enter the Magic restricted cell to hold a knife at a defenseless Cobra's neck. The stones appear to be sturdy as an explosion from Tartaros' Jackal was inefficacious, although it demolished the entire Magic Council Headquarters. Albeit, prisoners can be easily released by outside forces, such as when Lapointe assists in the Oración Seis' escape with his Personification Magic without the Magic Council noticing. The sealing stones also come in the form of handcuffs and shackles, which can impede the person from moving while also nullifying their Magic. The sealing stones can still be affected by Magic, as seen when Gômon was able to magically manipulate the sealing stone handcuffs and Gray was able freeze and shatter them.
In the anime, the cells adapt a relatively different appearance. Replacing the stones is a transparent, diamond-shaped glass. The cells appear to be smaller and are able to levitate in midair. Regardless, the effects are the same. Magic Sealing Stones come in variety of different items as well, such as ropes which the Guild Diabolos used.