Sigourney Weaver's name is practically synonymous with Sci-fi Scream Queen, and while she's had plenty of success with dramedies too, her true bread and butter has come from fiddling with the various fantastic film worlds filled with things like killer aliens and then some nice blue aliens and gooey ghosts and even robots with hearts! You get the gist; she's got a way with weird.

And, at least when compared to its contemporaries in interest, Cassie Clare's YA hit series "The Mortal Instruments" kinda goes there when it comes to strange stuff, like a maybe-maybe not brother and sister pair making out hardcore all the time and best friends turning into rats and motorcycles flying through the air and faerie queens spiking drinks with you-cannot-ever-leave-'til-I-say-so potions and such. Frankly, it's right up Weaver's alley, so if she's gonna do the teen scene ... and so it is. Weaver's now joined the cast of the second entry of the six-parter, "The Mortal Instruments: City of Ashes."

According to The Hollywood Reporter, Weaver has joined the pic, which begins shooting in Oct., as Imogen Herondale, the leader of the Shadowhunters who's got a big bone to pick with the series' archvillain Valentine Morgenstern (Jonathan Rhys Meyers) over her son's death. Operating under the new assumption — SPOILER ALERT about "The Mortal Instruments: City of Bones" — that Jace Wayland (Jamie Campbell Bower) is Valentine's son, she locks him up and holds him hostage to try and get to her target, thereby causing a whole buncha drama.

What's interesting about Weaver attaching to this role in particular is that — again, spoiler alert for those who haven't read the book — it's kind of a one-shot character rather than re-appearing across multiple installments, as one might expect for an actress of her caliber. Then again, Sigourney Weaver is the kinda gal who's willing to own a one-scene cameo for the right flick ...

... so maybe it shouldn't be so surprising after all.

Movie one in the series, "City of Bones," hits theaters on Aug. 21.