Spirits are divided up into different ranks: Over, Major, Minor, Demi
Each rank can gain the power from only a certain number of artifacts before they don't gain anymore: Over - 5, Major - 4, Minor - 3, Demi - 2
Each rank has a basic power level: Over - 30, Major - 12, Minor - 4, Demi - 1
Each artifact gives +2 to that.
You start with your Over and add 1/2 the power level of everyone working with him.
These don't really apply anymore though since the rules aren't really being enforced.
Romans 8:31 What, then, shall we say in response to this? If God is for us, who can be against us?
1 Corinthians 13:1-3 If I speak in the tongues of men or of angels, but do not have love, I am only a resounding gong or a clanging cymbal. If I have the gift of prophecy and can fathom all mysteries and all knowledge, and if I have a faith that can move mountains, but do not have love, I am nothing. If I give all I possess to the poor and give over my body to hardship that I may boast, but do not have love, I gain nothing.