Arch Enemy vocalist Alissa White-Gluz spoke in an interview by The Jasta Show, describing the process of joining Arch Enemy. She said:

It was in 2013, and Angela and Michael [Amott, guitar] from Arch Enemy had asked me if I wanted to join, and so I said, ‘Well, can I keep doing the band that I’m in?’ [referring to The Agonist].

And they were, like, ‘Yeah, we want you to be happy, so if you want, we can work out a schedule where both bands can be fulfilled.’ And in my head, at that point, I had already been spending a lot of time with Kamelot [touring as a guest vocalist], so I was, like, ‘Oh, well, with Kamelot, I’m just a guest. They can replace me easily.

So I’ll just stop doing Kamelot and focus on Arch Enemy and my current band.’ ‘Cause that band was my baby. I built that band, I picked the name, I drew the logo, I directed all the photo shoots… You know, it was my band.”

She also describes the dismissal of The Agonist as the greatest betrayal she has ever experienced.

That was the worst betrayal I’ve ever felt in my life. They stole a lot from me. It was not right. I know because fans have told me, ‘Hey, they’re saying this about you, they’re saying that,’ and rather than sinking to that level and actually presenting the truth… which I had to do at one point with the manager because he was actually being really rude to me and did not understand the situation.

And finally, I was, like, ‘Hey, I’m gonna forward you every e-mail concerning this situation.’ And then finally he read those e-mails and understood that I was the one telling the truth. And then he stopped working with them. Because he was, like, ‘Woah, wait a second. I was lied to.’ And it wasn’t by me. That was the only time that I’ve had to really be, like, ‘Okay, I’m just gonna stand up for mysef and prove the truth here.’ Otherwise, I just took the standpoint of I’m not gonna say anything negative about those people. I’m not even gonna talk about them at all.

They’ve stolen enough from me. I’m not gonna let them steal any more of my energy. Instead I’m gonna put my energy towards the good things that I have, which is from this point and into the future.”

You can read entire interview from here.