Immured anchorite

Tibetan monk

An immured anchorite, considered by many to be a myth, is a Tibetan monk who has taken a vow to spend his life permanently sealed inside a small walled cell. The walled cell, only large enough for the monk to sit in meditation, has only a single stone that is moved to offer bread and water once a day. The cell has no windows and the monk spends his life in complete darkness.

This keyword could refer to multiple things. Here are some suggestions: