Half-dragons, like all other half-breeds, are the combination of two particular kinds of creatures - in this case a dragon and something else.
Half dragons gain lesser versions of the physical and magical abilities of their dragon parent and some of the abilities of their non-dragon parent as well.
For example, a Sideron-elf half-breed would have tough grey skin and a weak magnetic field they could emit and focus (either as a breath, beams from their eyes, or generated from their hands as the player decides). They would also have the elfin affinity for nature and magic, and higher agility potential.
Half-dragons are an accepted part of dragon society on most worlds, though they do not exist on Majarcania. These rare individuals are often prominent members of the societies of their other half as well as their heightened abilities make them well suited from leadership, public service, adventuring, or in some very rare instances - high-powered villains.
Base Characteristics Edit
As many dragons and other kinds that they are capable of breeding with, it is impossible to provide a meaningful template. Instead, start with the non-dragon half as a template and then upgrade those characteristics based on the dragon half in your campaign.