Voodoo or vodoun was a religion.
In 1915, Gilles Lemaitre used the vodoun ritual of Wete Mo Nan Dlo in an attempt to restore Cthulhu. Before he could succeed, the Seventh Doctor managed to set explosives in the tomb which killed Lemaitre and resealed the Great Old One. (PROSE: White Darkness)
Grandfather Paradox was called the "voodoo priest of the House of Lungbarrow", He was imprisoned in Shada. When the Carnival Queen threatened rationality throughout the universe, Lady President Romana had an epileptic fit during which she signed a release order for three hundred prisoners, including the Grandfather. (PROSE: Christmas on a Rational Planet)