What is the significance of the ''Valar Morghulis'' phrase?

The phrase 'Valar Morghulis' is a significant part of the Game of Thrones universe. It is a High Valyrian saying, which translates to 'All men must die.' It is often used by characters in the show and the books as a farewell or a reminder of mortality.

In the story, the phrase is associated with the mysterious and deadly cult of assassins known as the Faceless Men, who believe that death is a gift that should be given to those who seek it. They are known to wear faces of the people they have killed, and they serve the Many-Faced God, who is the god of death worshipped in the Free City of Braavos.

Throughout the series, the phrase is used by many characters and serves as a reminder that death is an inevitable part of life. It is also a reminder that no one is safe in the world of Game of Thrones and that anyone can die at any moment, regardless of their power or status.