Just came across the Errant identifying Triban Gnol as the poisoner. In DoD Chapter 3, the Errant was gloating as he strangled Brys in the alley.
I warned you, Brys Beddict. This time, there will be no mistakes. Yes, it was me who nudged you to take that mouthful of poisoned wine—oh, the Chancellor had not anticipated such a thing, but he can be forgiven that. After all, how could I have imagined that you'd found a guardian among Mael's minions?
This time, instead of a nudge, the Errant opted for the body slam.
It's possible that more than one person added poison, but the Errant doesn't mention anyone else.
This post has been edited by Azath Housecat: 12 December 2015 - 10:40 AM