Board Thread:The Panopticon/@comment-4028641-20151008023030/@comment-1783865-20200106193843

Missy definitely had turned good by the end of her era before being struck down. So whatever Sacha's Master did discover about Gallifreyan history and the Timeless Child, it was definitely what made him a murderous psycho once again. I highly and strongly doubt Missy just changed into Sacha's Master and decided to be an insane lunatic again.

But of course until something like this gets explained in-universally, we can't add that to their history/timeline.