"The space inside the tomb was later occupied by an early Christian hermit. Fellows noted that the backs of the reliefs still bore the remains of the hermit's religious paintings and monograms. Fellows speculates that this man was a disciple of Simeon Stylites (390–459 AD), one of the eponymously named Christian ascetics known as stylites, who lived on the top of tall columns." (Wiki on Harpy Tomb), "... becoming a bastion of Christianity where strange Byzantine ascetics known as ‘pillar-saints’ moved into the old pagan tombs." (see link)
See storiesfromthemuseumfloor.wordpress.com

Church of Saint Simeon Stylites