This was the Amethyst Behemoth's inherent skill, Breath Locking. By releasing spiritual power and capitalizing on the Amethyst Behemoth's royal aura, it could sense if Beastmen were present within a certain range depending on the strength of the spiritual power. This skill could only be utilized after Zi had advanced to rank 8; otherwise, Glacis, the War Behemoth, would not have escaped detection back at the Ice Ring.
Zi's spiritual power was very strong, surpassing most of the non-Spiritual Attribute rank Nine Magical Beasts. Naturally, this was due to the same-life contract that allowed him to benefit from the increase in Ye Yinzhu's spiritual power.
The Breath Locking quickly concluded, and although it was the first time Zi had used this skill, he had a clear grasp of the exact locations of all the guards within the courtyard walls. Gesturing inside with his hand, he detailed his assessment of the guards to Ye Yinzhu through their mental connection.