The Covetous Demon was once a man whose deep affections were unrequited. The Bone Scythe indicates that he was entranced by some perversion of love by Mytha, the Baneful Queen. We know it is Mytha because the description states that he never left the Queen’s side, and we find him within the Earthern Peak along with Mytha the Baneful Queen. As an expression of desire for the Queen, this man ate excessively. Eventually, he transformed into the Covetous Demon, which only made him lonelier than before.
We know that Mytha was once considered the fairest queen in the land, but her love was unrequited by the man she eventually married, likely because it was a political marriage. However, to try and seduce her husband (perhaps due to her vanity), she experimented with poisons found in Harvest Valley, and eventually transformed herself into the gorgon-like woman we fight.
To be at the Queen’s side at all times, the Covetous Demon must have been an important member of the Queen’s court. It is likely he was wealthy before he transformed, as constantly eating is a characteristic of those with plenty. Therefore, it may be that he was an official of the Queen’s court before she was married, and fell in love with her there. Alternatively, it may be that when the Queen began to experiment with poison, this man who would become the Covetous Demon fell in love with her and all but confirmed that she should continue down her path if she was to win back the heart of her husband. We know that the Queen used poison to beckon unknowing souls to the defiled valley and perhaps these souls were entranced with some perversion of love, a description which may be referring to lust.
The Bone Scythe is said to grind flesh apart as opposed to slicing it. This is clearly indicative of the Covetous Demon’s teeth, which would grind apart its food, whether that is flesh or not. His eating is an expression of desire and he devours all things, even Undead Labours. This taste for flesh seems to link this demon to the Demon of Song, a demon which also developed a taste for flesh. While the comparison is interesting to note, it is perhaps just a common trait amongst demons.
The fate of the man who became the Covetous Demon is not unique. We also find a white colored Covetous Demon in the Lower Garrison of Eleum Loyce. The reason for this is never explained. The white Covetous Demon drops an Ivory Warrior Ring when defeated, either indicating that it ate a warrior wearing this ring or that it was a warrior who wore this ring before transforming (likely the former).