Board Thread:General Discussion/@comment-1.40.59.59-20160717064827/@comment-4010415-20160718035338

In Players and Pieces, when Weiss made a ton of glyphs to help Ruby drag the Nevermore up the cliff, you can actually notice Weiss bend over and start panting like she tired herself out making all those glyphs. In End of the Beginning, we're shown Glynda using her telekinesis Semblance to put pieces of a building back, and then she bends over and pants while the pieces fall back down. So, it looks like using your Semblance can use up Aura.

I think that when you run out of Aura, you can't use your Semblance and can't use Dust either. However, if you have magic, like a Maiden, you can still use your magic, as shown by Amber.