Petro is a magic that is parallel to to Voodoo, but is much more powerful. It has long been associated as a branch of Voodoo. This is an incorrect interpretation. The fact of the matter is that while Voodoo and Petro are similar in fashion and style, they were developed in two separate places at roughly the same time. This is even more of a testament to the power in the magic that has been interpreted as Voodoo and Petro respectively.
While Voodoo is a practice of peace and light, Petro was developed in Haiti and reflects more forceful and angry tones. They venerate the same deities and call upon these deities for the same magic. However, the magic is far more powerful because it uses the emotion of anger, meaning the magic comes and goes with a vengeance. This isn't saying that all of the magic that is developed by Petro are malicious or bad. It's just that they are developed with by a deeper emotional means, so the magic is that much more powerful.
The fact of the matter is that for so many years Marie Laveau has been referred to as the Queen of Voodoo. This is true in one respect, but also untrue. If we are to label her correctly, we would actually call her the Queen of Petro. This is the form of magic that she was originally brought up in and the roots to which she holds true. Laveau was very passionate about her magic and very emotionally involved. It is easy to see that she was actually brought up on Petro, which was later confused for Voodoo.
Make no mistake, Marie Laveau did practice Voodoo as well. It was more of a crossover power that she got into later in life. This was mostly because that's the magic that was being practiced by the people around her in New Orleans. Her roots lie in her Petro magic, however; which is far more powerful than anything she did with Voodoo.
Since Marie Laveau made mostly Voodoo pieces later in life, her pieces that were made using Petro are very rare. This is one of those pieces. The story about how we got this piece is very long and drawn out. The important part is that we have it. This piece holds Petro energy that has been placed into it by the great Marie Laveau. When you use this piece, Marie Laveau shows up to you in full soul form. This is more like a bi location of her physical self, because despite what the history books say she is not dead. She is immortal and very much alive. This piece brings a bi location of her in soul form. You can ask her for any power that you want and it will come to you in the form of Petro magic.
This magic has been specially developed by Marie Laveau and it is very easy to use. When you summon Marie Laveau, she will give you a Petro energy form. This energy form becomes merged with your own being and fused into your DNA. For instance, if you ask her for the ability to find true love, it will become part of who you are. You can use this power indefinitely to either benefit yourself or others. This is just an example. You can ask for any power and it will be granted to you, in Petro form, for you to use forever.