Theurgy is basically religious magic performed by ordained clergy within the Church of the True God (including both the official Church and splinter sects) and the Pantheon of the Old Gods.  These rare religious leaders posses such powers as healing, telepathy, levitation, telekenisis, and even shoot bolts of lightning from their limbs. 

Theurgy is said to come from the True God or other deities.  In the Old Universe, only Shi'ar and a few Saurians were known to have performed theurgy.  In the Pocket Universe, a number of Humans and a few Sontarans have been known to have exercised religious magic.

Similar powers are conducted by Psionics.