PREAMBLE
In the Marvel Universe, the Vodu are a pantheon of gods native to Western Africa and the Niger River valley, though their worship extends far beyond that region. Like the Asgardians, Olympians, Heliopolians and more, the Vodu emerged on Earth after Demogorge consumed the corrupted Elder Gods, who degenerated into demons, and redistributed their godly essence throughout the plane. The sky-father Buluku of the Vodu mated with the Elder Goddess Gaea and produced twins named Lusa and Mahu. They in turn mated and produced many more gods, commonly emerging as paired twins in the pantheon. Over time, many of the ancient pantheons of gods on Earth were displaced by the worship of modern religions. Worshippers of the Vodu, however, incorporated elements of Christianity into their culture without forsaking the children of Buluku in their prayers. Their followers brought the practice of Vodu worship, also known as vaudois, vaudou, voudoun or “voodoo” to some, from West Africa to the Caribbean and beyond.
The Vodu Gods themselves were aided and supplemented by the Loa, a collection of entities that acted as minor elemental spirits. In some circumstances, particularly powerful voodoo practitioners or restless dead could ascend to be considered Loa after their deaths as well. The twin gods Legba and Eschu served as masters of the Loa, often coordinating the dissemination of 
favors to grateful worshippers from the gods through their Loa. However, particularly in the Caribbean, worship was also directed towards Sagbata and Dam-Ayido Wede. Able to cultivate greater cultural prominence and therefore worship in the new world, these darker gods became known as Damballah and Baron Samedi. Though not inherently evil, these Vodu Gods were more indifferent to the impact their gifts would have on mortals, so long as the proper sacrifices were first made by their worshippers.
In the 17th century, a French freebooter named Captain Tyger campaigned against Spanish ships in the Caribbean with his free men companions, the twins Laurent and Alexandre. Tyger viciously opposed slavery in the region, and often crossed swords with the slave trafficking pirate, Boute-Feu. In seeking revenge, Boute-Feu ambushed Tyger’s men and killed Alexandre, taking his body to a voodoo priest named Shango. Boute-Feu wanted an invincible army of men who would obey his demands without question, and so Shango petitioned Baron Samedi for aid. Samedi in turn reached out to the surviving Elder God known as Chthon for even more power, and Chthon worked through Baron Samedi to grant Shango the magical spell that turned Alexandre into Earth’s first zombie. [Doctor Strange, Sorcerer Supreme #17]
Other zombies soon followed, and Boute-Feu had his army. He attacked Port-Margot and was 
opposed by Tyger and Laurent. Legba and the Vodu felt Sagbata had gone too far, and they intervened. The might of Chthon reinforced the zuvembie spell, however, making it too strong for the Vodu to break. Instead, Legda crafted a new form of power and bestowed it upon Laurent, making him the first Lord of the Loa, able to call upon those elemental spirits against Boute-Feu and his zombies. With the probable aid of Gaea, Legba also gave Laurent his ultimate spell, enabling him to free the spirit of Alexandre from its zombie prison and join with it. With this new power, Laurent broke Shango’s casting of the zombie spell and Captain Tyger killed Boute-Feu. The spell for zombies would spread throughout the world and return countless times in the future, but the title of Lord of the Loa would also pass down through generations to combat voodoo when it was used for evil, and the power would always be in the best hands when wielded by twins. [Doctor Strange, Sorcerer Supreme #20]
Centuries ago, the Vodu God of Iron and War called Ogoun the Slayer threatened the material plane. Papa Legba, the current Lord of the Loa, and Makeen the Sorcerer Supreme stood firm at the Gateway of Bondye, driving Ogoun back into the ever-dimensions where the Vodu Gods resided. They sacrificed their immortal souls to bind the gateway shut. From that point forward, the Vodu could not walk the Earth themselves, without opening the gates and risking Ogoun’s war reaching Earth. Instead, they were forced to rely upon familiars and lesser spirits as their representatives, granting their influence to petitioners, but never again their presence. [Doctor Voodoo: Avenger of the Supernatural #3]