Initially, the blood of dozens of ancient wyrms was required for the power of the Conquering Mageweath to be exerted to a greater extent. However, Lin Li didn't know where to get that many ancient wyrms whose blood he could drain. Fortunately, the Dragon of Destruction not only contained far more blood than dozens of ancient wyrms, the mana in its blood was also unique in Anril. Thus, it was the best substitute.
On the other hand, the flesh of the Dragon of Destruction was placed under the Sky Castle. The lower side of the Sky Castle was just like an inverted mountain peak, whose defensive ability was much inferior to that of the top. This was one of the crucial reasons that the Sky Castle had once been struck by the Sky-breaker.