Easy
The process was far easier than anything Ryu could have imagined. But as time passed, he wondered why it was he had thought that it would be a complicated process at all.
These furious Heaven's treasures, capable of changing the landscape, upturning the earth, and causing devastation the likes of which could completely alter the ecosystem of a world, had all been laying in his Realm Heart completely docilely.
They had long since lost sense of the methods that Ryu had used to trick them inside, and yet not a single one had fought back against him.
Thinking even further back, whether it was the Infinity Mist or the Origin Flames that formed his first to Beyond Perfect Extreme Cosmic Seeds, both had formed quite easily.
Origin Flames were on the more docile side to begin with, but was Infinity Mist? It should have long since shredded him to ash, but that hadn't happened at all.