Dear Lord Voldemort,
Yes, I am well aware that you are indeed dead but please do pretend you are still alive and not killed by Harry Potter. Oh, I see, it's a touchy subject for you, is it not? Well, let's not linger on unhappy memories. The real reason I'm corresponding with you is to convince you not to smoke. Believe me, it pains me greatly to be penning this letter to you, but it's a matter of schoolwork, and for that reason, I must oblige (and no, my name is not Hermione Granger). So begins the reasons not to smoke:
In addition to numerous diseases such as emphysema, lung cancer, chronic bronchitis, et cetera, et cetera, you will also have to deal with the following: extreme addiction to nicotine, deep wrinkles when you're only in your twenties, and nose and throat inflammation. Not that you need to worry about the last one, as you have no nose whatsoever, but just so you are aware. Contrary to many people's beliefs, smoking is not cool. It will lose you your respect and your friends. I see no reason for you to tear out your non-existent hair out on that one, as the meter on both of those is ticking close to zero. Short term effects are the simple, unimportant facts like that all your blood vessels will constrict, your heart rate and blood pressure will increase, and more stomach acid is produced, as the nicotine tricks your brain into thinking it's time to eat. Long-term effects include all types of cancers, wrinkled skin, dental diseases, and reduction in immune system effectiveness. I understand that those listed above are probably as trivial to you as can be, O-Mighty-Dark-One.
To conclude, please, do not ever try a cigarette. If, say, Bellatrix pressures you to just take a small drag during one of your evil plotting sessions, saying that it will ease the stress and perhaps keep the evil lord's-block at bay, firmly and assertively say no. It might make you look wimpy, it might make your Death Eaters snigger at you behind your back, but in the long run, it'll be worth it. Do you want your health or do you want people to laugh at you? I think the answer is very clear. Besides, it's not like you won't kill them when you get bored anyway.
Sincerely,
Gella