Who she is: Whitney Frost, a.k.a. Agnes Cully
Her power: Frost is a genius-level research scientist, but after being subjected to an explosion caused by Zero Matter that transferred mysterious Darkforce energy into her body, she developed the ability to absorb other people into her body by transforming them into Darkforce. As she mastered its power, she could even send Darkforce out to attack others, or use it as a method of torture without killing the victim.
Her story: As shown in Marvel’s Agent Carter, Frost was born Agnes Cully, and she grew up in Oklahoma with a single mother in a small home, where she developed a passion for electronics and science. During her teenage years, she moved by herself to California, where she was discovered by a talent scout and began acting, soon becoming a marquee name, and eventually marrying business Calvin Chadwick. However, she continued her research, eventually creating a powerful reactor that led to the discovery of what Frost named Zero Matter, an unstable compound that, after being told her work would be shut down, Frost attempted to steal. She was thwarted by Jason Wilkes, who was simultaneously trying to steal it with the help of Peggy Carter. The Zero Matter container shattered, infecting both of them; after discovering the extent of her power when infected, Frost attempted to open a portal to another dimension, which would have unleashed massive amounts of Darkforce that would’ve consumed Earth. Fortunately for all of us, she was stopped by Peggy Carter and others in the SSR. The encounter with Zero Matter drove Whitney Frost insane, and she was sent to an asylum.
Played by: Wynn Everett; Ivy George (as a child); Olivia Welch (as a teen)
Currently, Whitney Frost is: Wearing a straightjacket, in a padded room in an asylum. (That is, going by the 1940s-era standards of Agent Carter; in the contemporary era, she’s probably dead.)
Where will we see her next? Given Agent Carter’s cancelation, we’ve likely seen the last of Whitney Frost.