Trial by Fire
It clicked for Ryu right then.
If he was a member of the Taboo Powers and he knew that his legacy was on the verge of being destroyed, but he wanted to leave something, anything behind, how would he hide it?
The answer was quite obvious to him if he thought about it for just a moment. He would probably leave behind one, maybe even a few Ruins. These Ruins would then have two layers to them, one being a façade, and the other being my real legacy.
The façade would leave behind a real enough legacy so that no one else would consider the possibility that it was a façade in the first place. But the second layer, where he chose his true inheritor, would be hidden quite deep and likely only to be found by those who both knew what they were looking for, and, as an extra added precaution, had affinity and a willingness to carry on his legacy.
Ryu couldn't help but think of the Nine Pillar Flame Sky God again.