When FCG first talked about the death of Dancer and his family, all he remembered was a one-eyed monster.

When Imogen attempted to probe his mind, she ran in to a block that was described as "a scar."

For no reason, I've taken the intuitive leap that Ashton is the one that killed Dancer at the behest of an employer, and that Ashton took pity on FCG (who wouldn't), and Milo "cast" Modify Memory with the tech based Artificer implications that have been made.

This was bolstered in a more recent episode where Imogen and FCG were speaking, and Ashton actively worked to change the subject of the conversation from his friends.

Being Critical Role, I'm sure I'm way off, but I'm going to believe I'm on to something until they prove me wrong