Though Seth was still using mortal qi, that didn't change the fact that he was a calamity-level cultivator and one at the second stage to boot.
With his strength Seth was invisible to all the creatures in the forest, one second they felt the need to bow and then the next the feeling was gone.
Though all he did was fly through the forest, Seth's actions agitated the several beasts in the forest, causing panic to seep into them.
The deeper Seth went into the forest, the stronger the beasts he passed by, and the stronger these beasts were, the more sensitive and panicked they were when they felt an unexplainable power that was way above theirs even if it was for just a second.
Eventually, Seth passed by a couple of rank 6 beasts, and these creatures spoked by the sudden feeling that had gripped them could not help but roar, and in the midst of their confusion, their instincts kicked in.