To get more indepth on the spiritual practices of the shamans. Basically the shamans don't cast spells, but appease spirits who are the ones who cast the spell. In short your bribing spirits so they get to do favors for you.
So what do you summon? Let the d12 decide.
1. Demonic Spirit
2. Damned Soul
3. Plant Spirit
4. Animal Spirit
5. Animal Spirit
6. Lost Soul
7. Lost Soul
8. Animal Spirit
9. Animal Spirit
10. Plant Spirit
11. Blessed Soul
12. Angelic Spirit
Nailing a angelic spirit means the appeasement will be cheaper one category. Demonic spirits on the other hand will jack up the price by one category. So what does the spirit want?
1st and 2nd Level Spells (Angelic Spirits will do spells for free at these levels)
1. Intoxication, Dance, and Herbs
2. Dance and Herbs
3. Herbs
4. Herbs
5. Dance and Herbs
6. Intoxication, Dance, and Herbs
3rd and 4th Level Spells
1. Sex, Possession, Intoxication, Dancing, and Herbs
2. Possession, Intoxication, Dancing, and Herbs
3. Intoxication, Dancing, and Herbs
4. Intoxication, Dancing, and Herbs
5. Possession, Intoxication, Dancing, and Herbs
6. Sex, Possession, Intoxication, Dancing, and Herbs
5th and 6th Level Spells (Demonic spirits will demand more)
1. Mass Animal Sacrifice, Dancing, and Herbs (Mass Human Sacrifice)
2. Animal Sacrifice, Dancing, and Herbs (Human Sacrifice)
3. Sex, Possession, Intoxication, Dancing, and Herbs (Blood Fueled Orgy)
4. Sex, Possession, Intoxication, Dancing, and Herbs (Blood Fueled Orgy)
5. Animal Sacrifice, Dancing, and Herbs (Human Sacrifice)
6. Mass Animal Sacrifice, Dancing, and Herbs (Mass Human Sacrifice)
Thankfully the shaman can banish the spirit away (aka cancel the spell), but doing so will anger the spirit. Which means bad luck and you cannot do rituals for as many days as the spell level.
EDIT: I will point out most shamans stick with low level magic for these very reasons. They also immediately banish demonic spirits cause they rather take the couple of shitty days than do any requests from demons.