Imprinting anything on an item with item power 400+ requires coiling wards, baleful fragments, or abstruse sigils and rerolling a stat on a 400+ legendary requires forgotten souls. Items that require these materials start dropping between character level 32-35 in WT1, but these materials aren’t available until WT3.
Someone is going to immediately jump in to tell me that I can get most of these from salvaging legendary items above item power 400, but there are two problems with that.
First, that doesn’t actually work despite everyone repeating that it does. I’ve salvaged dozens of legendary items with item power between 400 and 600 and have not gotten a single one of those materials.
Second, it makes the Codex almost useless right at the time that you actually start needing those Aspects on many classes and then you’re stuck with whatever drops for the next 15 levels or so while you slog through the campaign and try to complete the Capstone with whatever random stuff dropped for you.
Then rerolling affixes on dropped legendary items is simply impossible until you get to WT3 because forgotten souls are only available in Helltides.