He is said to have a liver ailment, perhaps cancer, but this is impossible to confirm. In public he sometimes seems tired, but he is not obviously ill. In any case, Mr. Asahara has been complaining publicly at least since early last year that his health is failing.

"My body is considerably damaged now," Mr. Asahara said in a videotape recorded just a few days ago and broadcast on Japanese television.

In the videotape he says he was infected with Q-fever, an obscure ailment first found in Australia, where he says airplanes sprayed his compound with the disease. Mr. Asahara compares Q-fever to the plague, but doctors in Tokyo said that its symptoms are similar to those of pneumonia and that it can be cured.

Perhaps because of his declining health, Mr. Asahara may be giving increasing control over Aum to some of his lieutenants. But some people suggest that Mr. Asahara's own illness and his confrontation with his mortality -- if his ailment is that serious -- have encouraged him toward a more apocalyptic vision of the future, and perhaps even toward technologies of extermination such as nerve gas.

Mr. Asahara increasingly has come to emphasize a Manichean vision of the world, in which good and evil are in a constant battle. He sometimes seems to see himself cast as the force that will rise up and destroy the evil --represented by the United States and Japanese Governments -- in order to save the world.

Many of Mr. Asahara's teachings are drawn from Buddhism and the occult, but he also emphasizes a Hindu god, Lord Shiva, whose role in Hinduism may bear an eerie connection to Aum's present interest in poison gases. Shiva is a god of destruction and creation, and his job is to destroy so that life can be renewed.

"Maybe he thinks of himself as a living Shiva," said Shinichi Nakazawa, a professor of religious studies who has met Mr. Asahara several times. "Shiva, you know, has two faces -- one is peaceful and one is destructive."