I'm not saying that the current master should abuse Asterion (definitely not), or that the Devs should give a detailed look into what that abuse entails (from previous masters, if it existed at all). I only wanted to address the possibility that it may have happened in the past, and if it has happened that it should at least be touched upon during the psychological therapy portions with Asterion (assuming they add that to the game, which I think they should).
I really don't want a graphic blow by blow depiction of any abuse towards Asterion, certainly not sexual abuse, but I think that (again IF it has occurred with past masters) it should be directly looked at during those therapy sessions. It seems unrealistic to just ignore what would undoubtedly be a very traumatic incident (or series of incidents) for Asterion, when the purpose of the therapy is to acknowledge the past forms of abuse enacted against him, and help him to move forward, and hopefully begin to heal some of his psychological trauma.