How many places of power are there and what bonuses do they grant you?
Solution 1:
I've found four. Circle of Power, Life, Endurance, and Vigor.
Respectively, they seem to increase melee damage, Vitality, armor value, Vigor regeneration.
I'll see if I can't get some definite values hammered in as well.
Edit: Okay, preliminary testing has provided some results
Circle of Life -- 2 Vitality Regeneration (out of combat) / 1 Vitality Regeneration (in combat)
Circle of Endurance -- 3 Armor
Circle of Power -- 120% sign intensity? (So maybe +.2, since I had 1 sign intensity before?)
Circle of Vigor -- +300 duration (possibly x2 duration)