Atlas was completely enveloped in flames. They touched his body from every angle, making their presence impossible to ignore.
From a first look, it was obvious that he had to be in a lot of pain. Even the greatest phoenixes eventually had to leave the trial when the pain became too much.
The Trial of Fire was formed through the purest blood essence of ancestral phoenixes. It was not just a flaming corridor, but a singular sentient entity.
It judged anyone and everyone who passed through its doors based on their affinity for the Dao of Fire, and when the limits of their potential began to show, the fire would become more and more aggressive until it was unbearable.
Atlas was also meant to reach this limit eventually. The Elder sent him into this trial because she knew that it was the best way to quiet the opposition.