Dwarves were one of the many creatures created by the Precursors. They were probably amongst the first few races that had the opportunity to work closely with their creator. All of their knowledge of creation was given to them by the Precursors as a present for being loyal to them.
Astaroth was already aware of this much. But what Thori revealed next made the Xyran doubt the history of his race as he knew it. Ever since he was a kid, he was told that some selective Xyrans were born with Mournblades. But what Thori stated was much different than the tale he had heard and accepted as truth.
While it was true that the Mournblades chose their owner, no Xyran was born with a Mournblade. They bonded with one later on and the Dwarves created these Mournblades under the instruction and guidance of the Precursors.
The Mournblades were supposed to be a present for the entire race of Xyrans. Just like the Dwarves were given the knowledge of creation as a present.
