Ras master could be the dragon father of fsm.
We don't know why the fsm was even born. Was it an agreement between both races, a secret love or a trick on side used on the other (both can shapeshift).
I believe it has had to be a trick the dragons used on the oni. Why?
Because an alliance would mean they already agreed to peace. Not fight over who gets the child if both side are one. And if they loved their child (eath other) why didn't they follow / join fsm in ninjago?
So one side decided to end the war they would trick a member of the other side into a fake relationship. In this case probably the dragon. Why?
Because the oni have problems in feeling things, meaning they are easier to get tricked into a fake relationship or even just had arranged partners based on power. Making it harder for them to deceive the dragons. Besides they already were the villains.
So what if one dragon. Eather on his own idea (most likely) or as an agreement, tricked one of the oni into getting a child together.
This individual would be old, powerful, evil, but on the same time have some compassion left. Maybe saying they believed if they could get a hyprid child they coul kill all oni and end the war. Having a "for the greater good" mindset.
This would fit why ras master is powerful, apparently doesn't plan to betray ras and knows so much about the source dragons.
It would also explain why the fsm was explained again and why ras captured wu. They need the blood of the son to free the dragon. Like how garmadon was resurrected. Lloyd is only 1/4 dragon. While fsm was 1/2 dragon just like wu. Maybe wu has even more dragon blood since garmadon had more oni. Making him the most likely candidate for such a ritual.
Besides if the merge has some deeper meaning, then the creation of the separate worlds by the fsm should get some relevance. What better way to tackle this history by someone who was there.
Lloyd is gonna meet his great granddad.















