From what this book tells me the land owned by the Tinki'na people was considered holy.
The land was holy because of many old rituals and cleansing magic they did and so the land was cleansed of any darkness.
Because the land was untouched of darkness the faceless man could only watch from afar and he could not enter the land or touch the people.
When the child named Seik'nia entered she may have weakened the land and as she grew she may have slowly deteriorate the blessings.
Because of this, with time, the mask men were able to break through and kill the people.
I believe that is why Seik'nia felt she had to return to the land and make a final blessing that used her life.
Maybe this one spot of land is still holy and if that is true then it is this one spot that the faceless man cannot enter.
Or possibly, just maybe, it might cripple him if he was to enter it.
From what I also read it was only her body was used to seal the wind, earth and sky spirits into the land and keep it holy.
That may mean her own spirit could be wandering the land somewhere, it could be possible that she is still protecting the land from the faceless man.
Maybe she was reborn.
Too much thinking Vivian.
Time for bed.