I've been seeing people talk about rerolling a latent sunder to automatically get -70 or the perfect roll let's say. I heard it was with a shard. Is this true? If so do certain shards correlate with certain sunders? Just curious, in case somehow I get a sunder drop through the absolute atrocious odds

yeah youll never need this information so dont be sad without it, but its basically simiilar to a rune upping or socketing recipe, I believe its like a fal rune or something in the 18-20 range, plus 2 certain shards I think and maybe a gem.

But yes I believe it includes worldstone shards