Knowledge of overmastery by the mastrels

[MasterK-Bob]

Do we know whether overmastery making you a more powerful sandmaster was known by the mastrels, and it was sort of a test to see who would push themselves that far while being warned not to, or did Kenton discover its effects? I presume it was just so rarely done, and then only by people who pushed the limits who already had a lot of power?

[+Harrycrapper]

There's no clear answer, but I have a theory that I never did a post for I can shortly detail here. I don't think the overmastery itself is what made sand mastery stronger. I think becoming more in line with Autonomy's Intent by breaking the rules is what did it. Looking at other magic systems, there seems to be a correlation with people who embody the Shard's Intent and how strong they are or how they get their powers. This is most obvious in Stormlight where Knights Radiant have to swear Oaths to do Honorable things and become more powerful the further they go with those oaths. In Elantris, the people who are chosen by the Shaod all seem to be Devoted to something. In Raoden's case, he's extremely devoted to the people of Arelon and is the most powerful Elantrian. In Mistborn, Allomancers usually snap when they experience(at least what feels like) a life threatening event. I speculate they snap because they become aligned with Preservation and wish to Preserve themselves. Assuming I'm right about all of that, overmastery was a test like you said, though I'm not sure if they knew what they were doing. Sand Masters get their powers from Autonomy, and to be autonomous, one must not be bound by rules. Ever since Kenton showed little potential in the opening scene, he sought to use the rules of the Diem and the rules of Lossand to make his place there. But, by trying to work within the rules of those systems rather than rebelling against them, Kenton ensured he would get no stronger as a Sand Master. Drile on the other hand, broke rules and cared little for the Diem's leadership and he was seemingly as strong as Kenton's father. Baon is one of the most autonomous people we've seen in the Cosmere and based on that scene at the end he's going to be an immensely strong Sand Master. One other thing I'm not completely sure of is what seems to be the upper limit Kenton reaches with the amount of ribbons he can control. It's possible that once he figured out that the overmastery rule was a test, it became a pointless test. Or he does just have an upper limit on his strength, possibly related to how much Investiture he has in his Spirit Web. 

[Honorless]

We don't have a definite answer as to whether or not they knew Overmastery could result in increasing the no. of Ribbons a Sand Master can control. Some people can just control more Sand from the beginning, as we see with Drile. It might very well be the case that there are other conditions one needs to fulfill in order for Overmastery to not just leave them unable to do Sand Mastery. That it was Overmastering that lead to Kenton being able to Master more Ribbons was also his own theory, but Occam's Razor.

Kenton theorized that the knowledge of Overmastering to get stronger as a Sand Master was controlled by the upper ranks of the Diem as a gatekeeping measure to maintain their power structure.

It might very well be that Kenton truly discovered it and the Sand Masters didn't know, after all Overmastery is very physically painful and dangerous, as extreme dehydration tends to be. The Diem hadn't really been put in a situation where someone might be forced to Overmaster for a while, so the knowledge might've been lost too, but the Diem is a very old institution and maintained it's martial traditions and hierarchy, so them being unaware seems unlikely. One can draw conclusions from Lord Mastrell Praxton and Kenton's relationship to whether or not the former would've kept this from his son, but that's not conclusive evidence.

Autonomy and her Avatars might've blocked the spreading of that knowledge, for all we know, or... they might've intervened with Kenton to give him more power (there were faces in the sky that were watching; plus other Shards have done similar stuff).

Edited May 20, 2021 by Honorless