EDIT 2019: This was very much an experiment. As such, it might be a bit unbalanced. I might return to this idea for an Eberron release for DM’s Guild. Stay tuned.
One of the experiments of the Daelkyr was to use their symbionts in an effort to create half-Daelkyr hybrids. These beings would live their every day life until dark visions of Xoriat and an alien mindset slowly took over their victim. Never at home anywhere and haunted by dark visions from beyond the void, the Half-Blood is a tragic being.
For the most part, half-bloods look like their parental race. Some have naturally developed symbionts attached to their body in some way. However, it isn’t hard for them to be hidden in some manner. However, some Daelkyr Half-Bloods are more warped by their dark heritage. These poor beings are more likely to go mad by their sick cosmic masters.