The best explanation i can come up with without future sight or the time shenanigans between shards is perhaps the Amdapori experimented on themselves or prisoners or beasts on what would happen if you infuse too much light into a being, and watching the slaughter/carnage that would follow, then deside that making golums based on said monstrosities would be great additions to fighting against voidsent/mhach. Also can probably assume Ascian involvement with the war of the magi so could very well get info from them.