Board Thread:Episode Discussion/@comment-24573226-20171012080158/@comment-26397825-20171014171446

I don't think it's meant to be a theme; they never said you had to be a Maiden to use the relic, only open the vault. So when you think about it, the Maidens match the location they're in - Fall for Vale, Spirng for Mistral, Summer and Winter for presumably Vacuo and Atlas. Which relic is where can be extrapolated from this, but if they moved around the relics it wouldn't be that big of a deal. The Maiden's would still be required for a specific vault door, regardless of what relic is inside.