I got a huge what if question for ya! Its an interesting "what if" timeline. So lets say Elise survived assassinating Germain and say a year later they find out that it was Shay Cormac, current Grand Master of the American Rite, was Arno's father killer. Healed wounds reopened in Arno's heart. How would Elise feel and guide for Arno for this revelation? I asked this with folks around here before and its such a juicy lore bit to talk about and boy it still naggs me hahaha!!!
Ohh boy this is going to be interesting!
So let’s say that one year after Germain’s fall Élise had already re-established her place in the Order as Grand Master and Arno had rejoined the Brotherhood.
First off I believe that had Arno found out the identity of his father’s killer, he wouldn’t necessarily want to go after him. Sure at first it would deeply upset him and he would even play with the idea of revenge, but his father’s death is too distant to him now and he had probably come to terms with it over the years. He might never have even met Élise again after that day, had things turned out differently. As a boy, the only thing that came down to him from the whole situation was that his father had been murdered with seemingly no reason, that he had to suffer the greatest loss in his life because of a stranger - so his perfectly understandable reaction was probably wanting to find him and make him pay. But later as an Assassin, having learned about his heritage and the war between the two factions, I think it was easier for him to let go of any grudge he might have been holding. He now understands that this is a dangerous game where people inevitably die, and that his father was aware of that as well.Another reason that makes me think he wouldn’t want to kill Shay is that he knows, if only from the way it has affected and changed Élise, how consuming the desire for revenge can be and he would be too afraid to fall into the same situation as her. It was hard enough for him to redeem himself after Mr la Serre’s death, and in doing so I think he finally made peace with his father’s fate as well.I believe that rather than revenge, Arno would seek answers, and Élise would fully support him in that. What role did this father play in this all? Could his death have been avoided? Did he have to die simply because he was in the wrong place at the wrong time?
Now back to your question; I suppose Élise didn’t really think about who might’ve killed Charles when she was so little. His death didn’t directly affect her, but she saw that Arno was suffering and even if her reasons were a bit selfish, she tried her best to take his mind off of him.Given that Charles was an Assassin, discovering that the killer was a Templar probably wouldn’t be that much of a surprise to either of them. What might rather come as a surprise to Élise is the fact that it was the Grand Master of the American Rite. As a Templar Grand Master herself she is perfectly aware that it would be a dangerous move to eliminate such a high ranking member of the Order, and after all the hardship she had to go through and the losses she had to suffer, she would not want to risk her position. On the other hand, as much as she would want to be a good leader, she knows exactly how painful it is to lose a parent. She was there for him when Arno was mourning and then lost both of her parents herself. I think she wouldn’t directly tell Arno what to do but would instead encourage him to look for other ways of compensation, mostly because murdering Shay and stirring distrust and chaos within the Order again would set back their plan to bring the two sides closer by miles. She would always try and push for the third way, just as her mother made her promise to do.That being said, she would still respect and be supportive of his decision in the end because she believes that everyone has the right for revenge and to shape their own fate. If Arno felt that his father would rest only if the killer met with his end, she would accept it too. She would understand it more than anyone else.
Anyway, this is just how I see it, it’s fine to disagree, we can never really be sure, can we? Thank you for the question, this was fun! I really love thinking about this kind of stuff so more questions are always welcome :)