Forerunner fleet weaponry 4

Adapted from emplacements used on planet-cracking siege platforms, the main cannon of Mantle's Approach fires a bolt of exotic matter accelerated to a significant fraction of the speed of light. The entire ship must reconfigure itself after each firing, but each shot has the power to buckle continental plates and utterly disintegrate even phase rotated fortifications.
(Halo Warfleet; pg.86)