Hmmm...well, if you're still looking to gain lots of XPs and level up some more, then I'd say you should finish the lair. However, if you're looking for insight as regards loot in the lair...IIRC there was not any special tresure in the lair other than...
***SPOILER***
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...a greenstone amulet, which protects you from all types of mind control.
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Now where did I leave that doughnut?!