According to TVGuide.com, actress Cynthia Addai-Robinson, another Spartacus alum, has been cast in the DC Comics Villain role as Amanda Waller. Robinson who played Crixus' lover, Naevia, will join her former co-star Manu Bennett, who currently plays Slade Wilson aka Deathstroke on the show. Manu Bennett was recently upgraded to series regular for season 2.
The role of Amanda Waller was previously filled by Pam Grier in Smallville, Angela Bassett in Green Lantern and CCH Pounder in the animated Justice League series.
Personally, she's just another pretty face and looks kinda young to play "The Wall" in my opinion. I was hoping for someone a tad bit older and more intimidating. I guess they're basing her on the new 52 version of the character from the comics which I guess makes sense for a show on the CW.