I understand the basics of D&D, but I don't know the specifics of level draining.

I've been under the impression that Sabine has been draining levels from Elan. For one, how many levels do you guys suppose he lost so far and second, how does he get them back? Are they permanently lost? Can he just permanently lose SOME of them? I mean, that would be kind of brutal since they take so long to earn! He must be virtually useless with his level dropped so much.

Thanks in advance.