Theurgy is an active identification with a god-form/deity and is ultimately a process of purification, surrendering sins/karmas, cultivating virtues that are resonant with the god-form/deity, and receiving the deity into the luminous vehicle/soul. This is an incredibly receptive and reflective form of magic and any successful performance of it I have witnessed or experienced has required extensive and prolonged periods of purification and ritual. There are two things that are happening. The operator is making their soul as the deity/godform while at the same time the deity/godform is descending down into the soul. This can culminate in an "assumption" where the operator takes on the deity in their physical vessel but that usually requires even more intense practice and isolation. In order for the operator to make their soul as the deity the soul has to be cleansed through things that resemble purification, personal trials, confessions, study, regular communion/invocation, as a way to make the physical vessel and luminous vehicle suitable for the deity to descend into. This is "lifting up" the soul to the deity. On top of this in order for the deity to "descend" there has to be intense ritual, mantra, in a consecrated space, using the correct materials/synthemata so the physical environment is of the same quality and nature as the deity. In regards to the planets there are plenty of prescriptions for the correct environments and synthemata on the grimoiric record. This part of the operation is how you get the deity to "descend".
The practice itself is incredibly receptive. it is an emptying of the soul, a process of cultivating stillness, and a willingness and surrender to the deity. It should feel incredibly cathartic and sometimes a burning sensation inside the soul. It is not the same as regular practical magic where it is a focused concentration and exacting of the will towards a goal, the entire process should feel like throwing yourself into a black ocean. To trigger the process all you have to do is ask the deity and follow its direction.
