-Punk Hazard (the forbidden zone).
The entire island had been engulfed by poisonous fog. A pungent odor filled the air, and thick dust and smoke blanketed the sky, leaving sunlight barely able to penetrate.
Sephiroth walked through the fog-choked town in his Satellite Shining form. In his elemental state, the poison had no effect on him.
And, out of caution, he used the photoelectric effect to interfere with visible light, entering Optical Stealth mode.
He had waited until all the Marines had withdrawn from Punk Hazard before entering the sealed zone in his elemental form.
Abandoned facilities and the wreckage of collapsed buildings littered the streets. Visibility was poor.
Sephiroth's Mantra could survey his surroundings in precise detail.
Of course, he could disperse the poisonous fog, but that might attract unwanted attention. To be safe, he refrained.
With all those precautions, he had taken playing it safe to another level. Even the Cautious Hero would have given him a thumbs-up.
"..."
Within Sephiroth's Mantra, the deserted town streets felt especially desolate. Some buildings had corroded and melted.
The First and Second Research Institutes had both been blown up in the accident.
The poisonous fog was essentially hydrogen sulfide (in the original).
That was why it had caused such a violent explosion, and the substance could not naturally break down.
The island's climate also lacked strong winds, leaving the toxic gas, which was heavier than air, trapped on the island.
However, oxygen in the air would slowly oxidize it, producing elemental sulfur or sulfate. That was also why the town's buildings were corroding.
At that rate of oxidation, though, it would take a considerable amount of time to "consume" all the toxic gas.
The highly concentrated hydrogen sulfide now exceeded its upper explosive limit, and oxygen here was extremely scarce.
So,