User blog comment:SigmaAlphaThree/100 Questions for the traitor Arkanov/@comment-7270135-20160103232532/@comment-7270135-20160117035839

I've never really done it before, but I tried with the old River by giving her False Memory Syndrome, but it was really difficult and didn't know how to make it work well. So that's the challenge with Eris, to make her issue believable.

Yep! After losing his own kid, he's given up hope that it's possible to save any of the sacrifices, which is why he was really shocked when River ran and survived.