Based on Various Mythologies
Oracles are created when fae grant humans a drop of power. The amount of power and the negative side effect is what makes them differ from wytches.
They are given the power of foresight and if they become strong enough they are able to look back in time as well. There is usually a "curse" (blindness/barren/etc) due to the incompatibility of foreign majik and human genetics though the life span is lengthened to that of a wytch