Modifying the body, in ways that denaturate their biological purpose, is against what Satanism is about.
Things such as cutting the tongue in half, sharpening the teeth, and other such extremes you see online are not in any way, shape or form to be done to yourself.
Speaking of tattoos, people had tattoos since ancient times, even a pharaoh has been found with tattoos. However, tattoos nowadays use ink that is toxic for the body, and Satan advocates for everything that is healthy for us and our entire being.
So instead, you should focus on improving yourself in all areas of life. To live as healthy as possible is the satanic way.