A Warp storm is a violent disturbance in the Warp, the turbulent dimension that underlies faster-than-light travel and all psychic activity. Where the immaterium is normally navigable with care, a storm churns it into a maelstrom of raw energy, rendering whole regions of space impossible to cross and cutting off the worlds within from the rest of the galaxy.
Such storms are stirred by surges of emotion and belief, for the Warp mirrors the passions of living minds. A great war, a wave of terror, or a mass outpouring of worship can lash the immaterium into fury, and the resulting tempest may rage for days or persist for centuries. During its height, vessels attempting to traverse the affected zone risk being torn apart, thrown wildly off course, or lost forever, and communication that relies on the Warp falls silent.
The consequences reach beyond mere isolation. A powerful storm can thin the boundary between dimensions, allowing daemons and other immaterial horrors to spill into reality and beset the stranded worlds. Planets sealed behind such a barrier may endure generations of darkness, their fate unknown until the storm finally subsides. The largest and most enduring of these phenomena have reshaped the strategic map of the galaxy itself, severing empires and swallowing star systems whole.