Do you think Chief has a Bornstellar geas? If you remember from Halo 1 when Chief was about to fire the Halo (this is where I believe it took place) Spark said this to Chief: "Last time, you asked me, if it were my choice, would I do it? Having had considerable time to ponder your query, my answer has not changed."
And near the end of the book Bornstellar/IsoDidact asks him this. Soooo......possible IsoDidact upcoming in upcoming Halos? Not him physically, but inside Chief's head. We also know Spark is still alive and seems to be back to his Chakas self so you think if Chief has that geas it will emerge when they meet again?