Sometimes I have noticed that Sora (or anyone else in my party) will be walking around with this odd grey wispy swirling thing around them. What does it mean? Is it a good thing or a bad thing?
It is a good thing. Someone cast an Aero-family spell. The spells have the following effects:
- Aero - Halves damage taken. Duration is determined by adding 18 to your max MP.
- Aerora - The above + damage on contact with enemies. Damage is determined by doubling your max MP value, and adding 6.
- Aeroga - Above + it will deflect some attacks.
Below is a picture of Aeroga in action.
Information taken form the wiki linked above.