Lu Xuan killed people as if he were just mowing down weeds.
A terrifying slaughter was taking place.
Lu Xuan's aura shot to the heavens. There was no need to even sense the aura with one's own will; the phenomenon was so obvious that one could see the sky shrouded in blood-red color with one's naked eye.
The existence of life was a combination of will, qi, and consciousness. Cultivators were far stronger than any common being in all three.
Even then, gauging someone's capacity or strength in any of that required probing with one's willpower.
For instance, if someone were to probe Lu Xuan's mental world with their will, they would be able to see a golden dragon in there with enough power to bring all under providence to the keel.