The Guardians Are Coming

The Guardians Are Coming is an achievement in Halo: The Master Chief Collection. It is unlocked by being killed in a manner which is unrecognizable to the game engine. When this happens, the game displays the message, "You were killed by The Guardians.

This achievement can be unlocked through many means. For example, getting killed by environmental objects (such as train on the Halo 2 multiplayer map Terminal) or scripted objects (such as the turrets on Snowbound or Brute landmines on Sandtrap in Halo 3) will unlock this achievement.

Trivia
The name of the achievement may also be referring to Halo 5: Guardians.