According to the book of the Acts of the Apostles, Paul in the last years remained in Rome testifying his faith in Jesus Christ and awaiting judgment.
The book of Acts does not state what happened to Paul. It ends roughly and in a hard way. We will never know what happened to Paul.
But Clement seems to hint that Paul traveled to Spain, to the “farthest limits of the West.”

Lao Tsu was bored with the life spent in the increasingly sophisticated and corrupt court of Emperor Zhou. So he decided to jump on a buffalo that would take him to the western borders of the empire.
Although he was dressed like a peasant the soldiers on guard recognized him and before crossing the border they asked him with pity to write a compendium of all his wisdom accumulated over the years. According to the legend, Lao Tzu wrote the “Tao Te Ching” for them and after crossing the border he disappeared from their eyes.

A few years after Bodhidharma’s death, Ambassador Song Yun of the Wei Kingdom saw him walking with a shoe on his head on the Pamir Mountains. Song asked Bodhidharma where he was going, to which Bodhidharma replied “I’m going home”.
Upon arriving at the palace, Song told the emperor that he had met Bodhidharma along the way. The emperor did not believe him, so the tomb was opened and it was discovered that it was empty and contained only one shoe. The monks in the court then said “The Master has returned home” and prostrated themselves three times: “For nine years he abode and no one knew him. Carrying a shoe in his hand he went home quietly, without any ceremony.”

Zen, Daoism, and Christianity are built on missing persons. That’s their final strength.