Harry nodded. "At the very start of this process I had to take a whole load of personal elements from my own body  ... hair, blood, skin, sweat, spit, urine ... you get the idea. Then I had to mix them all together with dashes of sulphur and mercury into what was, in all honesty, this quite disgusting putrid mass. But it was my base matter ... all my life forces, as well as my cast-offs and my waste. I infused it with my magic and it formed a semi-solid, amorphous blob."