: The geas thing has grown on me. Now Spartans arent just Spartans because of
: their genetics, theyre Spartans because their genetics are a product of
: the Librarians millenia long struggle to uphold the Mantle against the
: Didact and the Flood.

but that's part of what I don't like

: After humans made landfall on Installation 04, geas began activating in
: humans, notably the Master Chief. The geas would give the humans a sense
: of familiarity with Forerunner technology. Even indicating certain buttons
: to press. For the Master Chief, this would continue throughout his journey
: on Halo.

: “The display’s shimmering geometric patterns nagged at him, as if he should
: recognize them somehow. Even with his enhanced memory, he couldn’t place
: where he’d seen them before. They just seemed…familiar. … He wasn’t sure
: why he touched the ‘button’ on the display. He just knew it felt right.”

: -Page 95, Chapter 3, Halo: The Flood DE

: The ability to detect which button to press on Forerunner hard light panels
: is a process described as instinctual. On a comparable level to the flight
: or fight response.

: “He seemed to know instinctively how to activate the panel–it almost seemed
: hard-wired, like his flight or flight response.”

: -Page 189, Chapter 6, Halo: The Flood DE

I know this was present from early on and might have even been sourced from Bungie, but it wasn't necessary, there was always the possibility that the panels had well-designed graphics that just weren't shown in the games, although that gets problematic for the Control Room.

: Encountering Forerunner technology on Halo would not be the only catalyst for
: dormant geas. SPARTAN-II Blue Team’s Fred would encounter a similar
: familiarity with Forerunner symbols in the Forerunner tunnels under
: Mechanite Mountain on Reach.

: “There was something too fascinating and nearly familiar about those
: symbols.”

: -Page 174, Chapter 15, Halo: First Strike DE"

I didn't know about that, that's a more solid indicator, even if it outside of the games.
The thing with both of these, though, is that it always seemed like a general sense that was put into humans, not a mind or a set of memories, which is what I understand a geas to (basically) be, and I was always under the impression everyone had this sense, this imprinting.
Come to think of it, why limit it?