Situation aspects can provide power facts. These can be established by characters using Create an Advantage, or naturally put in play through narration or the GM.
For example, a cleric's Holy Circle of Devotion can have power facts like "Repels demons or possessed beings" and "Blocks attempts at mind control". These power facts would affect anyone inside the circle. A vigilante's Smoke Bomb can have power facts like "Blocks light-based attacks" and "Exposes holograms".
Characters who frequently reuse the same situation aspects should work out their power facts in advance. They can also suggest power facts for aspects they've just created, if it makes sense to do so.