in each crate you get between 1 and 10 medallions which are doubled for all access members right now you can get medallions from the daily overseer crate quest (buy for 0c from arabella in FP or Qey harbor, ask a guard) or you can buy from marketplace cobalt crate category current is blood ember crate (for dbC) or you can search the broker and see if some are on there (for plat) or you can use your monthly stipend of 500 dbc to buy 10 crates (good deal)
OK so i can't buy blood ember crates for medaillions. I can buy crates for getting medaillions I have to get 7000 medaillions or 3x2 (for all accsess = 6 medaillions) = 1666 chests .. seem crazy for me