Lord d'Tornn takes another pull off his mug of dark ale and says "I heard that Abynnon is in town, and even stopped by to introduce himself last night. The fact that he did is as much an invitation as you need to pay a social call on him, and he is one of the more respected Initiates in the area. I'm not sure where he stands, but the fact that you were attacked by a Choker will likely influence him somewhat. He hates the Cults of the Dragon Below with a passion that transcends all reason, and you know the saying about the enemy of my enemy. If he could be swayed to help us he could be a tremendous asset.
If you have some way to build the Vault without disturbing nature too much, that's also sure to please him, and if he has no objection, many common people and Gatekeepers will go along. Not to mention the fact that Abynnon is likely to know where sites are in the area that meet your criteria. All in all, I think that he would be an excellent place to start."