Inner voice = the prime mover. Also inner voice = prima materia = first matter. It’s a part of the bigger order and doesn’t focus on human whim. I do what the voices tell me.
On to why you might practice invocation. There are two basic reasons. One is that when the spirit responds it shares its perception with you. Allows you insight you wouldn’t otherwise be privy to. For a period of time, you see as the spirit does. The other reason is that if it’s called for, you can act with the powers of the spirit you called. They are often powerful healers among other things.
On a related practice, they call it sorcery and is related to talismans among other things. In sorcery, rather than allowing a spirit to share in your power/energy, you call it into a foreign agent, a tool or other medium. So a ritual dagger becomes the residing place of a familiar spirit, say.
I had a spiritual teacher and was given a specific practice, or as you call invocation. I am a Bhakta. Oh, then you seek communion regularly. Bhakti yoga has invocation at its core. It is unlike other more mainstream religious practices though, in that it has an almost exclusively personal focus.
Personal in the sense that the practitioner has a personal relationship with God or Higher Power. It is like the lover to the beloved. The most recent avatar was a disciple of Kali. He was not adversarial to any other devotional sect nor are they to each other in general. He was just noted for having routine “ecstatic” moments where he would commune with the Great Mother, and was believed that from these he gained great wisdom.
Is Buddhist deity meditation a type of invocation? It is, yes, and in fact invocation does not need to be of a literal spirit. A sufficiently powerful thought form or symbol can still be the focus of invocation if the power of it is clear enough to the invoker. This is why the Buddha statues have to western eyes such strange postures and details. These conveyed necessary information to the student who was seeking communion with that Buddha.
Those are indicators, like our ki’i. Yes, exactly.
Your thoughts are welcome. Be well friends.