Eldarion

[The Saucepan Man]

This could be interpreted differently, but I think it is saying that Dior was an elf

However he is referred to, Dior had mortal blood in him. And so he was mortal. Anyone with mortal blood in them is mortal, unless offered the choice by Eru (thorugh the Valar). Dior was never given that choice. Of those with mixed mortal and immortal blood, the only ones who were offered the choice of immortality were Earendil and Elwing and their line.

Eldarion would never have had the choice, since the blood in his veins was purely mortal (as Arwen chose mortality), even though it was part Elven too.