Aura may be a way to describe

boosted fighters.
But more likely, just a fancy term to get the fans hooked... Like, I think it mainly started with Jiri Prochakza talking about Alex Pereira doing ritual with some "shamanics", getting spiritual help... Jiri mentioned "everyone can feel his energy and what's around him" as if it were an anime. Their face off and all, and the after fight in which Jiri got up but fell again once looking at Alex gave more fuel (tho mostly in a messing around way, but also... An intriguing one) to the "magic" stuff.
Izzy would talk about that as well before Alex came, and would mention it in his saga vs Alex Pereira...
And also, an interview from Aspinall that went viral in which he told something he felt when him and Alex sat next to each other pre UFC 295 (the one Tom got the interim belt and Alex defeated Jiri the first time).
Tom said his dad had asked him how was it sitting next to Alex Pereira, and Tom said "he thinks he can beat me, you know". His dad was like "what do you mean?"
and Tom — "Idk, I could just tell. We didn't talk much if at all, he seemed a little frosty when we met, definitely not happy chatty, it must be the language barrier. But as I was in the press conference [vs Sergei], I definitely could feel off him... He wasn't trying to intimidate me or posture, nothing, and I'm not that insecure guy. Maybe my mind was just making that up, idk, but it's almost like a feeling I'd get from an opponent. That's why when I heard he wanted to move to HW and wanted to fight me, I wasn't surprised... I definitely felt like he was sizing me up a little bit"...
So yeah I think it started moreso with Izzy at first but gained traction with Alex Pereira but unintentionally by his part, the comments made by Jiri Prochazka and Tom that kicked it in more so imo.