Although the recipe is significantly different to the oil created in Morytania, this oil serves a similar purpose. The priests of Emberwood created this oil to assist in funerary rites, the strange scent of the oil would help the dead pass on when cremated and, crucially, in the time of the Withering, the bodies would be reduced to ash, unable to get up and cause further trouble.
Originally this oil used pressed olives, and the influence of the gods to create an oil that would burn a body sufficiently to avoid the dead rising. As the Withering increased and civilisation began to fall into ruin, the priests found alternative methods to create a sufficiently strong flame.