Board Thread:General Discussion/@comment-1.40.59.59-20160717064827/@comment-26397825-20180106130316

I think it's a mixture of both.

You can use your semblance at the standard level as long as you have active aura. However, as soon as you try to push your semblance beyond what you're used to, it draws on your actual aura levels and drains it. This is what happened when Sun tried to pin Ilia down with his clones - not only did he summon more clones than he had ever summoned before, he also had them stay around for longer than ever and exert physical force on something.

Hence he drops to his knee we see his aura sort of become wispy and disappear, and why Ilia was then able to stab him in the shoulder with her sword.

It's like a muscle. You can use it as much as you like as long as you're only doing the same sort of actions that you always do. As soon as you try to push it, to use it beyond what you're used to, your energy drains quickly and you end up fatigued. Practise lets you do more with the muscle, and it can handle more stress before you are left fatigued. I think the same applies to aura and semblance.