Banishment

Yes, tens of thousands of years ago, Roy chose to become the person, or rather, the demon who led Sargeras to see the power of a Void Lord.

Since he would become one of the three commanders of the Burning Legion in the future, Roy knew that he would definitely cross paths with Sargeras, who had yet to fall, and the establishment of this relationship would inevitably take a long time. Moreover, because Roy was a demon, in order to prevent himself from being directly eliminated by Sargeras, he had to be cautious. Not only did he have to protect himself, but he also had to have enough capital to attract Sargeras's attention. So after he thought about it, the only entry point was the Old Gods.

In Roy's opinion, Sargeras might have come into contact with Void power at this time, but he might not have seen an Old God. Not only Sargeras, but all the titans of the Pantheon might not have enough understanding of the Old Gods.