i am trying to do The Ritual right now, but am having a hell of a time getting one of those ritual skulls to die. the ones that force project and level drain me. i get them to near death, but they never die. feel free to spoil me if it explains why they won't die. thanks in advance.

Not so spoilerish becuse Pontifex told you that you have to kill all the guardians around the skull before killing it.
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The problem you have is that some of them are invisible and maybe you havent't killed them yet. Just go around a little and they will attack or "True Sight".