Scarlet Witches - Is Agatha Harkness Tacked On?

I think that at the core of wanda, agnes is one of the most important characters in scarlet. She's not ng that they came up with later the they thought about that and lik, i don't know,. i totally disagree that she feels tacked on ut like, from the perspective of a marvel fan who's familiar with the idea. But to us, we have no idea who this person is. We know agnes, but it's like, really, the person you thought was agnes is really agatha harkness, a very powerful witch who's a bad guy.