Guardian Sentinel

The Guardian was a Forerunner Sentinel located at the Ark. They bear a strong resemblance to the S'pht Compilers from Marathon and the Forerunner hologram in Epitaph.

The Guardian Sentinel was originally set to appear as a fighting enemy in a campaign level that later became a multiplayer level Guardian but was removed, and featured in The Art of Halo 3 instead. It was stated that the player would have been able to rip out the Guardian's eye beam and use it as a weapon in the campaign level.

Although this Sentinel was cut from Halo 3, two Guardians are seen escorting a Keyship to the Portal in Origins.

Two similar looking sentinels are seen in the second level of halo 4 just before starting the third mission. Those sentinels are seen before numerous Promethean knights appear.