A favorite for assassins who prefer a more explosive means of death these letters are enchanted with a specific damage dealing spell and is delivered to targets delivered to targets  

The letter requires knowledge of enchanting items as well as the following items

• Paper or parchment that can be used for wizard spell books
• Wax for seals infused with the targets blood 
• A single quart of the maker's blood 

The letter is then enchanted with a damage dealing spell such as fireball. The spells deals double the damage that it normally would as well as causing the target to make any saving throws to avoid the spell at  disadvantage 

If anyone breaks the seal used to close the letter who does not have the blood of the who's blood was used to make it the spell is defused until the target or his/her next kin touch the seal