Davin Tyrell was the resentful brother of the rightful Duke of Daggerford. He was also the the godfather of Leonard Swiftfeatures. Along with his henchman Sycaran, he hatched a plot to murder his brother, then framed the Dragon Friends for the deed. (This was their own fault, as they were rightly detained on suspicion of Leonard's murder.)
When the Dragon Friends killed Sycuran during It Like She Me (1.02) they found an incriminating note:
Sycuran, my most loyal and trusted henchman, I have travelled with the delegation to Waterdeep. Appearances must be kept in front of the Grand Inquisitor. My hold on my brother's title is tenuous [...] Make sure that my friends do not survive to meet the Inquisitor. I entrust you with this as I can entrust no-one else, and I will see you when it returned.They later encountered him in Waterdeep.