Classic Garb of the astral warden

Hi, so i recently started playing ( shadowlands is my first expansion) and I heard that you can go back to old expansions and play those... I saw the garb of the astral warden and wanted to use that as my first transmog as it looks really cool (of course feel free to suggest other cool transmog stuff for my night elf druid). Anyway i think its in legion if i'm reading the wiki right but heck its confusing. I was wondering what expansion and raid i need to go do to get that set? via /r/wow https://ift.tt/3hwHgFz