In the pilot episode of The Vampire Diaries, there is a recurring motif of unnaturally creepy fog and crows at several points in the episode. Both are usually accompanied by something bad happening.
Eventually we learn that both of them are being caused by the first season's villain, Damon Salvatore, presumably for dramatic purposes. As quoted in this question:
STEFAN: Crow's a bit much, don't you think?
DAMON: Wait till you see what I can do with the fog.
As far as I know, after the first few episodes, neither of these things ever gets mentioned again: Damon never conjures this fog, or controls the birds, ever again, but neither does he explain why he can't or doesn't. The whole issue is just dropped.
Out of universe, I assume this was just an element of the pilot that the writers borrowed from novels (where Damon and Katherine can both control the weather), but decided wasn't working. But was there ever an in-universe explanation given why Damon's magic powers just vanished?