Edgar Waltz, was the main antagonist of the Grimm episode "Cat and Mouse" as a Hunjager (a hound dog like creature) he was a enforcer of the verrat (a secret organisation set up to keep the wesen under the royals comand)
Edgar chased Ian Hamond (a resistance leader) to Portland, there he began a murder spree, trying to route him out. He first went to talk to Captain Renard, seeking the Royals assistance, but Renard refused. Waltz warned him that his superiors weren't pleased with Renard's activities and to be wary of the Verrat, as they would remove him if he became a problem. Using his sources, Ian hunted down the resistance members in Portland, posing as Ian. He then murdered them, framing Ian for the killings, so that the police would be hunting Ian as well as him. Upon meeting Nick, he realised he was a Grimm. As Grimm had occasionally helped the Verrat in the past, he organised a meeting between the two.
He then finds another Resistance member, and threatens to kill his family, if he doesn't help him track down Ian. He then goes to the meeting with Nick, to discuss Ian. He threatens to continue randomly murdering people, unless Nick helps him find Ian. He then gets a call from the resistance member, who tells him about Rosalee hiding Ian. He leaves, and then kills the resistance member to cover his tracks.
Following Rosalee he first posses as a customer, then holds her hostage, threating Monroe that if they don't give him Ian he will kill her in fifteen minutes. When the fifteen minutes were up, Nick emerged claiming to have Ian, however then Monroe arrived making the same claim. The two began arguing, confusing Waltz. He thus unprepared when Monroe revels his true. In the confusion he's knocked down, and Ian shot him, finally killing the murder.