From Halopedia, the Halo wiki
In the later years of the Forerunners' war against the Flood parasite, Dutiful-Marcher and several other Warrior-Servants were assigned to Seclusion Spiral, a gas mining station on the gas giant Seclusion. One day, while on patrol in Vane One with Capital-Enforcer and two other Forerunners, they encountered the Flood. Soon after the encounter, Dutiful-Marcher was turned into a combat form. Capital-Enforcer quickly reported in and received reinforcements, one from each of the other three patrols currently on duty. Capital and the other Forerunners engaged the combat form. When it suffered too much damage, several infection forms burst from him and attacked Capital and the others.
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