[ At some point in early February, a parcel is left for Darin at his forge. It's clearly marked as being from Emet-Selch. Past the simple wrapping and the box itself, is...what initially looks underwhelming: it's an elegantly refined piece of cloudy white crystal (tetragonal prism, left). There's a note accompanying it. ]
Keep this near wherever you create or inset those elemental materia into your weapons. It can measure the latent magic of your surroundings and warn you if it exceeds a safe threshold. It will glow a most blinding white should that happen and attempt to absorb the excess magic. Once it cannot hold any more, it will shatter. You should have evacuated yourself and any others with you before then.
Gift
Keep this near wherever you create or inset those elemental materia into your weapons. It can measure the latent magic of your surroundings and warn you if it exceeds a safe threshold. It will glow a most blinding white should that happen and attempt to absorb the excess magic. Once it cannot hold any more, it will shatter. You should have evacuated yourself and any others with you before then.