Well, I have used all but 1 Wild Artefact, and Vile Peaks 010AF is the final one I need...so it must be in Academia 4XXAF, since that is the only place on the Historia Crux with any closed gates left --- I think I know, I don't think I know. I don't think I know that I know. I think I know even though I don't think I know. I don't think I think.
Go to [Grand Avenue] in AF4XX Academia, visit Chocolina's shop and activate nearby crystal gate with Wild Artefact. It unlocks AF010 Vile Peaks timeline. --- The first complete English guide to Final Fantasy XIII-2 is here! http://www.gamefaqs.com/ps3/619315-final-fantasy-xiii-2/faqs/63553