Which graveyard? The graveyard district or the graveyard in Trademeet? If you're talking about the graveyard district, I think I might know what you're talking about. When you're sent to kill Bodhi, you have someone else come with you to kill her (3 people, Drizzt is one of whom they can be), and I'm pretty sure that person is the one who opens the door. I can't remember to clearly about it though.. I may be wrong.