Lord Pendleton's Reward is a written note found in Dishonored.
Transcript
This matter with my brothers has not been pleasant at all so I don’t wish to discuss it further. However, I really must thank you. I’ve heard that you found some other means of neutralizing them, without taking their lives. Ingenious. Wherever they are, even if they are miserable, they are alive at least. So perhaps some day I will see them again.
Location
If Corvo employs Slackjaw's non-lethal elimination of the Pendleton Twins, this note and several gold bricks can be found in Corvo's quarters immediately following the mission the Royal Physician.