Wizards are dangerous types, and can cause a tremendous amount of damage if they know what they’re doing. Beginner spellcasters who have no idea about the extent of the arcane have the potential to be even more dangerous in some cases. Write about an aspiring mage who just can’t get things right.
Ideas and questions:
While the impetus has been put on the aspiring mage to make the mistakes here, it could be that a storied sage is just as at fault as their student. If they’re not paying enough attention, perhaps spells could go wrong, or alchemical reagents could be used disproportionately. It could make for a fun comedy between two arcanists (or more).
The location in which the events take place could drastically shape the story. If your aspiring mage is casting magic in close quarters, they could damage the room. If they are in a forest, they could start a wildfire.
The level to which things go wrong can vary depending on what sort of story you want to tell. But the prompt evokes the mage perhaps taking on more than they should. Perhaps they are trying to impress someone—a mentor, a potential love interest, a family member.
Does this mage have a mentor, or are they learning magic on their own? If so, how are they learning? Through the use of a book, through watching other magic users from the shadows, or something else entirely?
Is this aspirant someone who has more confidence in themselves than they should? Or is it a situation where they don’t have any self-confidence at all, and it is affecting how much control they have over the arcane?
Learning magic is hard enough. But you could make it all the more challenging by increasing the difficulty by which the aspiring mage must study. Perhaps there is a linguistic problem between them and their mentor—a speech impediment, a different dialect, even another language—or perhaps there are sensory differences between the student and their master. Write your story with some additional obstacle in the way for the aspirant.