Dragons breed, and not just with other dragons. Out of instinct, lust, strategic concerns, loneliness, curiosity, or even rage, dragons spread their seed and beget offspring of all shapes and sizes. Dragons also spill blood—theirs as well as others’—and their blood is potent. Myths speak of its power to curse, heal, or grant rare abilities, and sorcerers and wizards covet it to experiment with. And dragons have a supernatural connection to their domains, slowly warping them and the animals therein in their images. All these factors make the existence of half-dragons not just likely but inevitable. The dracolisk is just one example among many of such creatures.
Black dragons are notorious for breeding with other reptiles in their swamps—in part to gain allies to defend their lairs, but mostly out of boredom. (Given that they hate other dragons, including other blacks, they are not much given to socializing.) Half-black dragon crocodiles and lizardfolk are thus somewhat common as such things go, and a wise black dragon will often coax or bribe his offspring into serving as guards or lookouts. Dracolisks are a different story. They’re far too ornery to serve as guards and far too dangerous to keep around. Typically they are a result of a juvenile black dragon’s first mating (basilisks are considered a dangerous but worthwhile “catch” by the randy young bests), and are driven from the dragon’s domain as soon as the shell cracks.
Parental expectations can weigh heavy. This is especially true for silver dragon offspring. The Iron Coast boasts at least two ex-paladin half-silver dragons who could no longer bear to carry on their parents’ crusade against evil. Recently one has heard rumors of an entire nation of half-dragons, and seeks companions to search out the truth.
The product of two truly evil souls meeting, a half-green dragon peryton adds a terrible cone of acid to its already formidable abilities. It is slowly bringing a flock of perytons to heel, and already holds sway over the local leucrottas, who it deploys as spies.
—Pathfinder Bestiary 170
Aside from the d20 mechanic itself, the template was, hands-down, the most revolutionary-yet-forehead-slapping, “We should have thought of this years ago” innovation delivered by the 3rd edition of the world’s oldest role-playing game. With the system’s monster design and math smoothed out, templates meant you could transform, advance, power down, and otherwise mess with monsters like never before. Nothing symbolized that more than the half-dragon. Of course, soon the half-dragon went from everyone’s go-to new monster to being totally overexposed, and as the game aged template fatigue on the whole set in. But enough time had passed that now you can work them back into your adventures without feeling sheepish about it…and maybe even make them a focus of your campaign.