Thank you to Jade-The-Kitsune for your character and question idea.

Dear Injudicious Muggle Who Has The Brain Capacity Of A Common Pack Mule,

As much as it displeases me to send a letter to one as low as you, I am in quite a fix. It all began a long time ago when I tried to kill this silly boy who was only one year old. I would never have picked him myself out of a crowd of about 300, but there was this...::warning lights start flashing, sirens sound out (very loudly) and Wormtail rushes up to his master's side whispering something in his ear:: WHAT?! Preposterous! They can't tell me, the Great Dark Lord, what to do! ::Wormtail continues to whisper:: Fine...very well. But, one of these days, I will reveal the secret of The Order of the Phoenix! ::Wormtail disappears into a corner:: Well, anyway, this THING told me to...do something with this boy...wait... that sounded really wrong...Ack! This THING told me to use some sort of magic on this boy but it backfired, almost killing me. So, I kept at it. For almost 16 years I have tried and tried to...cast that SPELL that this THING told me to on this boy but I have never succeeded. Even now, when I am back in my original body, I cannot defeat him. Even during that terrible fight in the...ALL RIGHT! ALL RIGHT ALREADY! Even during that fight in the PLACE where wizards are, I could not put this SPELL on him that this THING told me to! Why can I not ki...err, put this SPELL on this boy?

Not Your Friend,
Evil Dark Lord Who Shall Kill All Muggles and Mudbloods And Finally Go Down In The Muggle Book The Guinness Book Of World Records As The Most Evil

Dear Gay-Ass MoFo,

::Snicker:: Having trouble wording our question, are we? ::Snicker:: Just because you are in the fifth Harry Potter book doesn't mean you can give away all of its secrets! Just because I have read it doesn't mean you can say them because of all the people reading this crappy advice column who haven't! HA! Okay, well, I'm sure a good 3/4 of you have read the book (being the die-hard fans that you are), but for those of you that haven't...well, you get the idea. So, anyway, are you sure that you listened to this THING carefully? I'm sure that you can do whatever it is that you want to this boy...you're right, that does sound wrong...you can do without a SPELL. You do know that most people (wizard and not) cannot survive falling off of a cliff, right? I'm sure that you, of all people, have thought of more ways to make someone kick the bucket than just a SPELL. Dumbass...

Sincerely,
SiriousB1