Geas

"This ring contains significant dangers, and even with your assumed legacy, I must verify the presence and pitch of your gei before allowing full access."

— 04-343 Guilty Spark in a transmission to the UNSC Pillar of Autumn

Geas (plural gei) was an archaic Forerunner term that referred to a generations-long genetic command imposed on an organism or species. Under the influence of a geas, an organism could be given a set of subconscious orders that would be passed on to their children, in some cases lasting several generations. Only highly skilled Forerunner Lifeworkers were capable of creating a geas. Forerunner students of the Mantle also hypothesized that the Precursors may have imposed a geas on the Forerunners themselves.

During her stewardship of Erde-Tyrene and humanity, the Librarian used an automated imprinting system to impose a geas upon several human family lineages, including those of the Florian Riser, who were imprinted with a drive to pass the defenses surrounding the Didact's Cryptum at the Djamonkin Crater. Riser's and Chakas' geas also included songs which served as codes to open the Cryptum, as well as deep genetic memories of their ancestors who fought in the Human-Forerunner War, including the long-lost secret for stopping the Flood.

The Librarian also imposed a broader geas on the entire human race, which has affected them a great deal throughout their history following the activation of the Halo Array. The geas included, among other things, memory impressions of their ancestors. In addition, part of the geas is that the basic image of what humans view as an ideal female is based upon the Librarian.

Trivia

In the real world, the word "geas" comes from a Scottish Welsh corruption of the Old Irish word "geis", which can mean "curse", "spell", or "command".

List of appearances

• The Forerunner Saga
  • Halo: Cryptum (First appearance)
  • Halo: Primordium
• Halo: Combat Evolved Anniversary
  • Terminals