Lena Marcinko is the main antagonist of the Grimm Episode "Tarantella" She is a Spinnetod, a spider like creature. As a female she is forced to eat three victims for every time she sheds her skin or else she is cursed to rapidly age.
Lena was married, and had a daughter, however to maintain her youth she was forced to eat three men every five years. She took no pleasure in doing this act, but went along with it simply to follow her kinds tradition.
By 2012 she had already killed three men ten years earlier in Albuquerque, and five years later in Phoenix. By 2012 she was living in Portland, and thus began her killing spree. She would dress up in some different attire. Seduce a man, have sex with him, then kill him. Regurgitate acid over him, and eat his remains. Her Killings, however hit a snag, when she chose another Wesen as a victim, although she was able to overpower and kill him, he still bit off her finger. Which led Nick and Hank to her. As a Spinnetod she had simply grown another by this point.
Realising what she was, Nick investigated Spinnetods, and realised she would murder again, for the third time. Nick managed to force her husband into revealing what he knew. And then tracked her down, where she was seducing her third Victim. Hank saved the man, while Nick took her on. Possessing spider like powers, she proved a match for Nick. Forcing him down she tried to make him her third victim. But Nick broke free, and threw her off, catching her (quite ironically) in a fishing net. She was arrested and imprison for murder. Unable to have fed, she rapidly aged to that of an old woman.