It sounds like a dish made up of things you only eat because they're disintegrated past the point of recognition...or I suppose theurgy could be some Ancient Greek philosophical concept (which means, of course, that it's been invented by someone not even clever enough to have worn trousers, avoided being executed by the authorities, or taught somewhere with a roof).
Theurgy is glutinous, dingy, inscrutable...
...except that it's not.
Well, not always.
Theurgy is when a god joins in with human affairs. Or it can be a miracle performed by such a god. Or it can be the good magic taught in Egypt around the 4th century AD.
It's a wonderful, exciting, sparkling, dangerous, terrifying thing...
...that sounds like congealed gravy.
Word Not To Use Today: theurgy. This word comes from the Greek words for god and work, theos and ergon.