The spell pronounciations?
It is literally* the case that BG3 will require the player to actually incant the spell into their microphone and if they get it wrong then bad things will happen.
* literally! †
† possibly. A bit. ‡
‡ Okay, not really. But I think they should just for a laugh.
FUZZ RADAHH!!

You know you can cast shouts on xbox when playing skyrim ))
But to be honest i think its actually one of those detail that actually differentiate BG from its competitors, i work as motion designer and in our studio we have a sound guy working only on sounds all day

Sound design is as important as graphic design, though many people dont realise it. I would sell their music for a good sound effects any day, you know why?? cuz i turn off music in most of the games after 200-300 hrs you heared enough, but you dont turn off sound of the spells ;))!!