Raze eventually stops regenerating, but it can take a while. You need to recharge while he is. Take potions, cast heal spell, etc. Also, this is a good time to use potions of strength, dexterity, etc. Boost your damage up by boosting the stat that you depend on. I'm a mage, so I take my most powerful intellect booster.
As far as Keara and the statues: Did you mindread Keara and learn that all the statues are lying? Armed with this info, the puzzle is a simple logic one. Devastation is the one alone. Havok and Mayhem share and so do Chaos and the other one, I've forgotten.
In the hall of echoes, you'll walk quite a little ways and then meet a ghost who warns you that you'll be facing former enemies again. You'll be fighting about 6 groups of enemies without resting, so this will be another great area to quaff some potions. Don't forget to summon your creature for the Raze/Keara/Echoes fights. He'll help immensely. Make sure that your creature is strong, where you are weak. I keep my creature as a melee fighter, because I'm great at range.
Hope this helps!
