From Halopedia, the Halo wiki
Filial Devotion was a Forerunner who lived during the time of the Forerunner-Flood war. The individual wrote a letter to their father which was visible on the seventh Terminal that John-117 encountered on Installation 00.
Filial Devotion's letter
Filial Devotion can be translated into "dedication to one's son or daughter" which could possibly reflect on the relationship Filial Devotion's father had with his child.
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