Witness Him Quest Walkthrough
This quest starts: After you complete the previous quest and talk to Alkibiades.
Description: You have to find the witness somewhere around Agora. Talk to the man – you can encourage him to cooperate with threats or money. You can also decide that the “citizen” is not worthy of his rights. Return to Alkibiades and report everything to him to earn 7500 XP.
Xp is level based, I received 14500 experience from doing it but I am also level 31.