I still have the savegame somewhere on the computer.
Battle result said it wasn't dead. There didn't appear to be a spell on it as it reappeared in an adjacent province as if it had retreated.
You can clearly see the fall bears killing the serpent. This has also happened with a dwarf smith before...poor guy used destruction one too many times on my mechanical men. Turns out...he was unable to move a few turns and got whacked...but didn't really.
Maybe AI troops get to retreat faster. I don't know. I'd be happy to email someone the file if they'd like to have a look at it and judge for themselves if I am imagining this. Just tell me where the saves are in the file structure for dominions.
