The expensive part of building fast boots in Diablo 4's Season of Hell's Legacy isn't finding a pair that looks promising. It's getting the numbers right. In the Season 15 crafting setup described here, Attuned Primordial Dust fuels the Horadric Cube's Affix Value Reroll recipe, making it central to improving your movement speed roll. If you're comparing D4 items, look at the starting affixes...