I have woken up with what I suspect is part of an Ars Magica scenario (official canon or fan made), and looking for the rest of it. Unless it is a dream, or some conflation from some other source(s).
A mage is flying above shadows/fogbank in the process of casting a spell when interrupted by (church) bells below. Left insensate, perhaps Temporary Twilight, the flying spell carries on for miles before failing and dropping the mage in a half frozen lake, wet robes dragging the mage below. Later in warmer weather the mage’s bones are discovered and properly buried. Rescuer is rewarded by talking wizard staff.