Dear Princess Celestia,
There's no delicate way to put this, so forgive me for being blunt.
With your permission, I’d like to further my necromancy studies, either on my own or under the tutelage of Princess Luna if she’s willing. I'm not asking because I enjoy it, I'm asking because I know I can do good with it.
Magic is neither good nor evil. It's a set of tools. I’m the first pony in centuries to expand upon established magic theory solely because I learned how to use a tool everyone else wanted to forget. And I'm still only an amateur. If I can master this tool, the knowledge I could apply to other fields of magic is invaluable. Even if I'm completely wrong and my knowledge of necromancy turns out to be useless for other fields of magic, I can still do good with it. I'm already doing good with it.
The Apples make their own fertilizer. They have a small compost bin behind the barn where they deposit some of their food wastes. The waste decomposes into a mulch they can spread over their crops. Decomposition is the final death of the body, so I've come to understand the process intimately. It's not much, but I was able to use this knowledge to enchant the bin such that it now alters the decomposition rate depending on the materials inside, resulting in a richer fertilizer.
Fluttershy spends the first two weeks of every spring looking for animals that didn't make it through the winter. Animals with young will sometimes starve themselves to ensure their offspring can eat. If the offspring are too young to fend for themselves, they will remain next to the body of their parent, eventually starving or being preyed upon. These are the bodies Fluttershy searches for. She takes in the orphaned animals and raises them until they reach maturity. I was able to help her this year thanks to my understanding of necromancy. The biological process of decay has a unique magical frequency, one I've become very familiar with. This familiarity allowed me to locate every recently deceased animal in Whitetail Woods in a matter of hours. Fluttershy now has twelve new mouths to feed, more than she's ever recovered from previous winters.
They’re little things, yes, but they serve as examples that necromancy can be used for good. And if you're still not convinced, remember that for a long, long time, teleportation was considered unethical due to it utilizing a process not too dissimilar to my cloning spell. Safe teleportation was thought to be impossible, but one stallion kept trying. He teleported over and over and over, tearing small pieces of his soul away until he had a complete understanding of how spatial displacement worked. He used this knowledge to create a new teleportation spell, a safe one. He took the tool everyone else threw out and did something good with it.
So I ask you again, Princess. Please, let me learn. I want to turn this into something good.
Your faithful student,
Twilight Sparkle