EW.com first reported Monday (Dec. 31) that the actress will appear on a recurring basis this season in the mysterious role of Tamara, who's described as a "charming and likable woman who’s secretly highly ambitious and a fearless leader driven to get what she wants."
The site reports that the new character may also return for Season 3, but there's no word yet on what Tamara's mythological identity might be.
Martin-Green's character Sasha was introduced in the recent "Walking Dead" midseason finale as part of a group of survivors led by her brother, Tyreese (Chad L. Coleman), who just discovered the prison. She's expected to continue on the series when it returns in February.
"Once Upon a Time" Season 2 resumes next Sunday, Jan. 6 at 8/7 p.m. CST on ABC, while "The Walking Dead" will be back from hiatus on Sunday, Feb. 10 on AMC.