Y'know, befriending Lareth the beautiful can be extremely useful to evil parties who want masterwork weapons.
Normally it's Spugnoir as well, who points out the location of Emridy meadows. Since your only reason for not asking Terjon where Emridy Meadows is, is due to yours being an evil-aligned party, I ought to mention that a NE-aligned party HAS to speak to Terjon as part of its initial quest - so I don't see the problem, really.