Talk:True Lab/@comment-135.0.167.68-20151023054645

So, uh, Undyne actually giving you the letter should be what triggers random encounters to completely stop. But if you kill something in the CORE before going to get the letter (or at least the phone call that tells you about it, that's what I did) (and also after Sans's judgement; that probably has something to do with it) you'll go on the date with Alphys and go through the True Lab. Asriel's fight still happens, the barrier is broken, everyone is saved; it is flat out the True Ending, but with murder.

I guess it might be self-defense, though; Sans wasn't really paying attention.

Since I don't know how Sans reacts, I don't know if killing one of the post-Undyne but pre-Asgore bosses will lock you out or not. Might have to try that next.