It was Agatha all along...

I guess my main questions would be:
So Billy, at the moment of mama Wanda blowing up the hex and erasing her children, used his powers to 'warp' into another nearby Billy who had just died...but how would Toby, errr Tommy, be able to replicate that?? I'm sure there is less of a 'logical' explanation for how Wanda decided to scour the multi-verse for the kids...instead of sensing her son in another person--like a few miles away...
The Darkhold twisted her mind. That's why she turns into a villain. It probably made her think they were out in the multiverse instead of somewhere else in this world.