Ninjago theory/headcanon: What if Mystake is the FSM's mother?
Other then stating that the FSM is the child of both Dragon and Oni blood, and the implications of the Firstborn. We don't know much about his heritage, and I don't see many people discussing it. Folks have been theorizing about who his children's mother is, if they have one, however no one askes the questions who the FSM's parents were. And he is practically confirmed to have two parents, he couldn't be a half-breed with only one parent.
So, this question got me thinking. Then while re-watching Season 9/Hunted I wondered, why did Mystake turn on her fellow Oni? If she said it was because she fell in love with NInjago, the FSM's creation, but why would she have looked that closely at something a glorified living weapon made. Unless she had a hand in making it.
We know that Mystake isn't above playing spy. What if the Oni sent her in to spy on the dragons during the war? However while in disguise, she turns traitor, falling in love with one of the Firstborn's children, or maybe the mother of dragons herself (The Oni are shape-shifters, Gender can kind of be thrown out the window). Leading to the birth of the FSM.
If this did happened, maybe Mystake managed to keep it secret and volunteered to be on the mission to capture the FSM after he fled. Wanting to keep and eye on her son. Or maybe the Omega sent her on the mission in order to prove her loyalty to the Oni after discovering she had turned traitor and had a half dragon child. Dubbing her, Mystake, or 'mistake'. So that every Oni would know her sin.
If the FSM was her son it would give her more reason to turn on her fellow generals, since she would be protecting her child. It would also explain the distance relationship she has with Garmadon and Wu. If she were their mother like people have theorized, she'd probably be more involved in their lives especially after the FSM's death. She doesn't seem like the kind of person to sit around and let her child be poisoned by a snake. However if she was more distantly related, like a Grandmother, it would make more sense. Likely it would be awkward for her to step in any more then she did, since the FSM probably spent the majority of his youth with the Dragons. It's an estranged relationship even if Mystake deeply cared for the FSM. Due to this distance its likely that she felt she didn't have much say in Garmadon's and Wu's lives. If they came to her, she'd help without question, but otherwise she just watches from a distance.
She only really gets involved in things when Lloyd, her possible great-grandson, doesn't have anyone else to turn too. Maybe she felt guilty about him getting wrapped in Tomorrow's Tea, Maybe she didn't want her family to suffer from her inaction any more once Wu was de-aged and Garmadon was mutated into something that reminded her of her people. Utter destructive monsters. Something she never wanted any of her family to become after learn you could be so much more in a world of peace.
On top of all that, her Oni form seems to share a lot of physical similarities with Garmadons, ei the white markings and rib structure, something even called out in the wiki, suggesting a genetic connection between the two.
Well at least that's what I figure. I'm probably incorrect, but its fun thought to chew on.
