Harbinger (achievement)

Harbinger is an achievement in Halo 5: Guardians, awarded for keeping Blue Team alive during the level The Breaking on Legendary difficulty.

Description
The achievement does not require that all of Blue Team never die; at least one member never dying is enough to grant it. The achievement will not be awarded until the level is fully completed, including the cutscenes and defeating the three Warden Eternals, meaning it will be granted at the start of Guardians.