Marvel Executive Director of TV Communications Arune Singh tweeted this from ABC’s presentation at the Television Critics Association meetings in Los Angeles Friday:
Jamie [sic] Alexander as Sif announced as guest star on #AgentsofSHIELD this season! #TCA14
Yes, Arune did misspell her name. No word yet on an airdate, the storyline or with whom she will interact, but this sounds pretty cool to me.