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I have never done evocation before but i have read up on it and i was wondering what spirits are safe to summon
That's like asking, "What guns are safe to fire?" It depends on how you hold it. Practice awareness so you aren't aiming at yourself.
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if you can just scry to see what spirits are in the area?
Short answer, yes. Long answer.... that involves a dash of ability, awareness, talent, calm mind, state of mind, attitude... You know what? I'm going to avoid talking too much, and just say, "Learn to see without seeing." If you can intuit things quickly, you can tell just by the vibe of the area, what kinds of spirits are around.