For the uninitiated, allow me to explain.
When referring to media, a trope is similar in meaning to the word "cliche," though it has a neutral tone, compared to the nearly always negative tone of the term "cliche." (So you wouldn't insult a scene or concept by calling it a trope, but you usually would by calling it cliched.) Basically, they're things that you'll see and recognize as repeating across media.
A trope deconstruction, meanwhile, is a piece of media that criticizes the unrealistic and usually far-too-ideal portrayal of certain tropes by showing it in a more realistic and usually much darker light. For example, if the popular works of the day mostly show the hero who never gave up winning and getting everything he wants without losing anything (think early Disney films), a movie attempting to deconstruct that trope would have an equally determined character's never-give-up attitude work against him, as he fights for what he believes in without backing down even when it would be smart, and he and everyone he cares about are much worse off than before (or even dead) for the fact. This is often done just to criticize the overshooting idealism of the initial works, though it's often also done because the writer genuinely believes the counter-message (for the above example, "just being determined to succeed doesn't always mean you will succeed").
So, let's play a game. Think of all the unrealistically handled tropes that happen in medieval-styled high-fantasy stories, and then think of how you can deconstruct them in an Ars Magica game. The more unrealistic the trope and the more realistic (not just dark, because more darkness does not translate to more realism, though darkness is juicy too) your re-interpretation of how that trope would play out, the better you do!
I'll start. There are a whole bunch of stories involving people who grew up as commoners finding out that they're actually royalty, and after doing some magical thing that can only be done by a true heir to the throne, they become king, and thanks to the compassion they learned from growing up as commoners, they become everybody's favorite king. If this were to happen in a realistic Ars Magica game, nearly any commoner who found themselves in that position would have no idea how to rule or manage the political climate, and would immediately want to take advantage of all the luxuries they didn't have before for personal pleasure, rather than using their funds and luxuries to help improve the standard of living for the poor. This would cause difficulties throughout the kingdom for about a month before one of the dissatisfied noble shmucks got their favored royal replacement set up, and then said king would be summarily assassinated, and the legend would be handed down for generations as an example of why it's better for everybody if the nobility and royalty are kept above and away from the taint of common people.
Okay, you guys' turn! Give it your best! If you need help thinking of tropes to deconstruct, there's a website with a whole catalogue of tropes as well as in-depth explanations of each an every one of them called tvtropes dot com. Let the games begin!