Horcruxes are the darkest form of Dark Magic. Horcruxes are created in a very complicated way, but the effect is that they root the spirit to the earth. Even if the body is gone, the spirit lives on. Here is how to make a Horcrux:

1. You must commit an act of unspeakable evil, which rips your soul in half.

2. You must choose an object, preferably one that has great meaning to you.

3. You must run your wand across your chest, from left to right, slowly, while using this chant:

4. Then slowly run your wand over the object, while chanting this: 

You are now immortal, unless your Horcrux is destroyed by:

Basilisk fang

Fiendfyre 

Goblin blade

The Horcrux has part of your soul, so you cannot die,