A hyper-grid intrusion (or gridfire) is the channelling of the energy grid into real space. It has a blindingly white appearance.
A similar effect may be achieved by crash-stopping from high speeds while using hyperspace propulsion.
By the Idiran-Culture War, both the Culture and the Idiran Empire had sufficient expertise with the grid to form gridfire.
Novalevel gridfire was used by the GSV Eschatologist to destroy Vavatch Orbital during the Idiran-Culture War.
The Dra'Azon used a weapon resembling gridfire to enforce the Quiet Barrier around a Planet of the Dead.
Gridfire was not witnessed in the Milky Way for at least 500 years after the Idiran-Culture War.