I'm at the end of the cult of the eyeless quest (I think). I'm in a small room with a holy altar, which contains (surprisingly) a couple of scrolls of small value and some gems of small value. There is a monster in the room called "Empathic Manifestation" who attacks you. He continues to say somthing like Hate and suffering, I feed on them....

Anyway I've been beating on this guy who has been at "Near Death" for half an hour now. So my question is.. how do I kill this thing? And how do I end the quest?

You're given a hint there. It thrives on death and destruction = weapons cant kill it. So kill it with love
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.heal it

He's right. The monster feeds on the bad feeling of the people, so fighting it with anger only keeps it alive. Use a cure spell on it, either from your memory or from the altar.

heheheh I wonder which genuise at Bioware thought of that?

The same one that walks around the office in a flower power shirt. Every company has one.