Petro god

The Petro gods were a group of loa in Haitian vodoun identified by Howard Phillips as the "evil gods". The priest Gilles Lemaitre was said to have been a sorcerer who practised the darker rites of the Petro gods from the Congo whose ceremonies could produce zombies. In 1915, people from villages throughout Haiti were afraid that Baron Samedi and the Petro gods roamed the countryside.

Lemaitre and his associates Carrefour and Henri Duval served the Great Old Ones, specifically Cthulhu. (PROSE: White Darkness)

Makandal created "new and hungry" loa of the Revolution in Saint-Domingue during the 18th century. (COMIC: Bêtes Noires & Dark Horses, PROSE: The Adventuress of Henrietta Street)

Hermes indicated a group of Immortals acted as gods in Haiti but didn't refer to groups. (PROSE: Deadly Reunion)

Behind the scenes

 * David A. McIntee's distinction of good and evil is not one used by most vodouisants. The Rada and Petro's rites are both used together and there aren't separate priests. Clairvius Dubois is as much a sorcerer as Lemaitre because he also produces zombies.
 * The phrasing in White Darkness obscures whether he means that the rites or the gods themselves come from the Congo. McIntee's primary source, The Serpent and the Rainbow, refers to them as being connected to the violence of the colonial era, not in any way to Africa like the Rada Loa.
 * Baron Samedi is a member of the Guédé Loa, a group usually held distinct from Rada or Petro.