Guardian Sentinel

Guardian Sentinels are a Forerunner construct created prior to the firing of the Halo Array.

Holograms
Holograms of these constructs were displayed in structures on Installation 00 and the Silent Auditorium of Installation 07.

Cortana's interpretation
By 2556, when John-117 and Cortana was stranded in space after the Battle of Installation 00, Cortana interpreted these constructs around Strato-Sentinels, and as escorts for a Keyship at the Portal at Voi during the Forerunners war against the Flood.

Production notes
The Guardians have a storied history with the Halo series, with their core idea dating back to the development of Halo 2. Notably, the Guardians were heavily developed for Halo 3, with many pieces of concept art created for their design. The Guardians were to feature in the eponymous level Guardian Forest as enemies, with a model and animations being created for them, and the in-game character in iteration. In the level, the player would have been able to rip out the Guardian's "eye" and use it as a laser weapon. Unfortunately, the level and the Guardian enemy had to be cut, with the level being repurposed as the Guardian multiplayer map and the Guardian enemy model itself used on Epitaph in holographic form. The Guardian was intended to be similar in size to the similarly-cut Strato-Sentinels. While not seen in the final game, their design was later used in Origins for two Forerunner constructs seen escorting a Keyship to the Portal at Voi. The Guardian hologram reappears in Halo Infinite. The Halo Encyclopedia (2022 edition) reveals that the holograms of the Guardian Sentinels were repurposed as in-universe holographic representations of Offensive Bias.

Additional information provided by Halo 3 Campaign Environment Lead Chris Barrett, who is cited as being the creator of the Guardians, reveals that the Guardian had two states, a regular and a "deployed" state, the deployed state being ultimately repurposed as the Epitaph hologram in the final game. Jaime Griesemer would also provide information comparing their intended movement design to that of the Compilers from Marathon.

Design documents uploaded online by campaign design lead Rob Stokes indicated the Guardians were considered at various stages of development to appear in some form in the levels The Ark, Guardian Forest, Alpine, Forerunner City, and Halo.

According to Art of Halo 3, "The Guardian evokes memories of Compilers (from one of Bungie's previous games, Marathon) and the robes of a High Court Judge - which is fitting because, as anyone who has encountered them can tell you, their judgments are swift and final, and their logic utterly alien."

List of appearances

 * Halo 3
 * Halo Legends
 * Origins
 * Halo Infinite