Sentinal Beam
From Halopedia, the Halo wiki
The Sentinal Beam is a weapon developed by the forerunners to help destroy flood.The sentinal beam was implamented on a floating machine called a sentinal. Sentinals are usally controlled by the Ai construct of their Halo ring.Sentinals were incountred.In Halo:CE the sentinal beam waas a unusable weapon.While in Halo 2 it was added to help fight the flood.