Indeed, the treasure Knight Shtad had discovered in the desert was a Citadel.
Not the Tomb of Ariel itself, of course — no scout had managed to get anywhere near the black pyramid, yet. It just always loomed far in the distance, never getting closer, like an ominous mirage.
But he did find a Citadel.
At this point, both Valor and Song were scouting the outer reaches of the desert in search of a suitable position to establish a base camp. Once they found one, numerous soldiers would be brought there through the corresponding Nightmare Gates, and the expeditions toward the pyramid would be launched.
However, a Citadel had the potential to drastically change the balance of power between the two great clans in their pursuit of the Demon's tomb.
The clan that possessed one would hold an overwhelming advantage. The clan that did not would fall behind before the race even started.