Just invis past the potemids. They don't see invis. If you are a non-caster then buy some invis potions...have a few, it tends to drop when you least expect it to.
I did have a few Temptress's see through invis. Was pretty rare though, still not hard to get to the place. If I recall, it is right infront of the queens room. Just be sure to con everything as you go, there are wanderers in the tunnels.