A Sphere - Prompt 17

There, between two broken cupboards in an abandoned and blasted home, hovers something completely out of place. A white sphere, about the size of a human head, is suspended in the air. Runes in an unknown language dance across the surface in an orange glow. Responding to touch, the runes shift and change across surface of the sphere.

What is this strange object, and why is it in the ruins of a home?