Staff of the Archmage

The Staff of the Archmage is one of the great pre-Inundation artefacts, spoken of in hushed tones through the early books as the instrument that let the Archmagi of the Magocracy rule. In Arcanist Lilastien finally reveals what it actually was: not a weapon, but an intelligence.

Lilastien explains the colonial-era grading of Constructed Intelligences — from Level One (simpler than Forseti's survey rover), to Level Three (Forseti himself, "about as smart as a human or Karshak"), to the Level Fives who were:

The most specialized and did things like running entire cities or scientific installations, directing colonial policy or commanding spaceships. They were almost as smart as an Alka Alon. Most of the serious problems arising in the later Colonial period were the fault of the Level Fives.Lilastien, Arcanist

And then, of the Staff of the Archmage specifically:

That was a particularly egotistical Level Five. In fact, the intelligence of the Staff of the Archmage was one of the central planning intelligences for the colony. It was once in charge of all of Leden City, on Perwyn, and was one of the few to escape the unpleasantness before the Inundation. While instrumental in re-forming the government, it was also ruthless in its administration. And that caused problems.Lilastien, Arcanist

So the "Staff" was an ancient AI that governed what was left of humanity after Perwyn sank, gave the Magocracy its institutional shape, and was eventually lost or deactivated before the Narasi Conquest. Its absence is one of the great silences in the history of humanity on Callidore — and one of the questions the IRIS and Forseti may yet illuminate.