The following are two pictures taken at the same frame, same event, but different trailers.
Here we see a "shield-like" spell from the "A New Adventure" trailer
Here we have the same moment taken from the "The End of an Era" trailer
Both trailers still depict a projectile being deflected from the "shield/fog". Regardless, it's not an ability that is present in version 1.0.
I was really hoping for a shield like spell that was depicted in the opening movie for the game and then when I saw the same spell being used again in ARR trailer footage I was really excited but this makes it really vague as to what the fate of this potential combat mechanic could be.
It's clear that whatever ability is depicted is meant to be a defensive one but it's unclear as to what that ability really does. It seems like it's really just an in-between version of Protect. It doesn't create a visible force field as seen in the "A New Adventure" trailer. The in-game version of protect will show a force field momentarily whenever you are attacked but is otherwise invisible while the "The End of an Era" trailer just creates a permanent haze around the character.
... I wish we could get a force-field like spell though.