It depends on how it was animated. Similar to ability auras is the hero glow.
Answering your question: give a bone to each plane and change the size(scale) it bigger or smaller in next frames. Also if you want it to disapper like the devotion aura you must set the transparency from 0-100% for visible and invisible part.
Devotion Aura doesn't expand. It makes like a wave. So maybe bones that change transparency. What I mean by wave is it kind of reveals to whole thing, but yes, it does wave outward at the same time