As a spell-writer, you're the magical equivalent of computer programmer. You've made and copied countless spells, but this is the first time you're desperate enough to try 'hacking' one.
This is extremely dangerous, but in the heat of a duel, you've got to try something.

You must target a specific spell of your opponents (no spells can be targetless), and you must have a reasonable chance of stopping it. To do this, you need to examine the original spell's text thoroughly.

When writing down a spell, you must choose exactly how many components it needs, what kind of components they are, and what the exact wording
In this situation, imagine you're trying to reverse engineer a spell that has been'stolen' from you. You've managed to obtain a scrap of parchment that's half-melted around the edges, and it reads:

_Maelum Quieta Cogita_
_Silence storms in thought_

You're confident this is the basis for a weather-manipulation spell, but there's no