Geas

"Installation 04 contains significant dangers, and even with human assumed legacy, I must verify the presence and pitch of your gei before allowing full access."

— 343 Guilty Spark

Geas 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.

The Librarian imposed a geas upon several human family lineages, including those of the Florian Riser and chamanune Chakas, who were imprinted with a drive to pass the defenses surrounding the Didact's Cryptum at the Djamonkin Crater. Their 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 wars, including the long-lost secret for stopping the Flood.

Trivia

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

List of appearances

• Halo: Cryptum (First appearance)
• Halo: Combat Evolved Anniversary