Heavy ion weapon system
From Halopedia, the Halo wiki
A heavy ion weapon systen is a kind of superweapon system employed aboard Forerunner warships. One such weapon was employed aboard the Mantle's Approach as its main weapon, adapted from emplacements used on planet-cracking siege platforms. The heavy ion weapon system fires a bolt of exotic matter accelerated to a significant fraction of the speed of light, with the power to buckle continental plates and disintegratre even phase-rotated fortifications. After being fired, the Mantle's Approach must reconfigure itself.