Board Thread:General Discussion/@comment-1.40.59.59-20160717064827/@comment-86.14.30.202-20161028161341

It's safe to presume that Mercury took her aura down to 16% and knew it. He's perceptive enough as was consistently shown in the series, so he knows just when to throw the fight. Furthermore, Flynt Coal also used his semblance while being in nigh-critical condition just like Yang did. Semblance doesn't consume aura.