Not all champions have auras.  If a champion has an aura it will always show up in their skill list in the champions view.  Some champions can’t use their aura until they’re ascended though(usually ascended three times). It will show three purple stars over the aura on the skull page if you need to ascend to be able to use it. Do you know how to ascend a champ?

Also, usually only rare, epic or legendary champs have auras so the common and uncommon champs you get at the start won’t have them.