[X] Yes, it would allow you to leave in a few days time without leaving the keep considerably weakened if no solution has been found until then -[X] Before Tyene returns to her mission in Slaver's Bay, ask her to speak with Morwyn and Tuin when she next sees them. The Drow assassins might be able to offer some insight into the poison, if they are familiar with it. Potential shelf life of the poison is of particular interest.