From Discworld MUD Wiki
Fire crackers are used in the spell Calm Embrace of Illusionary Beauty. They can also be lit and optionally thrown to the ground.
This is a large red fire cracker of Auriental manufacture. It's the sort of thing that is thrown at weddings. You may 'light' it, and 'throw' it. It appears to have something written on it. You read the fire cracker: Written in Agatean: ACME Firecracker
A fire cracker takes around ten seconds to explode.
If you're carrying it when it explodes, you get this:
light fire cracker You light the fire cracker and smoke begins to pour out. [time passes] The fire cracker explodes in your face! Meep meep! Your face feels heavy with soot and you're sure your hair has been charred!
This doesn't do any damage, but does add a line to your description:
She has a heavy layer of soot covering her face, and her hair is charred and singed.
You can also throw it to the ground or drop it, in which case it simply explodes on the ground.
- Firecracker, which works in a very similar way but is cosmetically different