Presumably Father Emperor thought the same way. By bringing Su Ziji in, he created a three-way balance, setting three men against one another. While stabilizing the court, it would also keep Prince Qi and himself "busy," preventing them from turning their spare thoughts toward the Imperial Palace.
Father Emperor's heart truly remained as it had always been.
Especially when he considered that Father Emperor, seated upon the throne, had always been cold and ruthless, yet knew how to make the utmost use of everything. Even the eldest legitimate son he had once favored—the Crown Prince of those years—could be erased outright once he infringed upon power. Prince Qi and he were merely Father Emperor's new chess pieces. These pieces were simply expensive enough that it was not yet time to discard them.
So long as he did not cross Father Emperor's bottom line, Father Emperor, following his usual conduct, naturally would not do anything to him.
At this thought, Prince Shu gave a self-mocking smile. "The more I once envied the Crown Prince, the more I understood, from the moment he was killed, that to Father Emperor, we sons have never mattered more than power."
Father-son affection was thinner than paper within the Imperial City—more fragile, too.
Yet he did not speak those words aloud. As he sighed, his hand unconsciously tightened around the armrest of his chair.
When the rabbit died, the fox grieved. Nothing could describe it better.
"The Crown Prince is dead. Does that mean we imperial princes are at peace? No. The Crown Prince's death was, in truth, a warning to us."
"Even after becoming Crown Prince, even with the status of eldest legitimate son and the mantle of orthodoxy, when the Emperor truly wished to remove him, he had no means of resistance at all."