Hrisskar Flat-Foot is supposed to be at Arrille's Tradehouse in Seyda Neen to give you the quest: Fargoth's Hiding Place. I finished the prerequisite quest (Fargoth's Ring), but now I can't find him anywhere. I've looked everywhere in Seyda Neen and talked to everyone.
Some NPCs in Morroblivion
Some NPCs in Morroblivion have AI routines set up, so they won't be in the same place all the time.
Happened to me also, I just
Happened to me also, I just reloaded my quicksave a couple of times and waited a few hours and he appeared.