I had an inspiration tonight and would really like to play it! So, here directly from my imagination is the awesome (at least I think it is) idea's setting and background:
There are two types of sentient beings, humans and dragons. Dragons were created long ago by humans using a lost ritual (rituals being the only kind of magic available to humans), by investing power into drakes (this worldís equivalent to horses. Dragons are huge beasts, being roughly the size of a house (when on all fours), plus tail, serpentine neck and wings and legs. They are sexually anatomically correct humanoids with breasts and vagina if female, a penis if male and draconic features. They stand on two legs (though they can use all fours) and have opposable thumbs with three fingers on their clawed hands. They wear clothes mostly for vanity as they do not actually need them.
Dragons choose a human as their mate. They donít bother asking the human and choose by whatever methods they think best. They bring the human to their mountain lairs and begin to change them. Females feed male humans their milk while males feed female humans their semen. This slowly changes humans so that women can accept a male dragonís massive penis within them and men grow their penises to the massive proportions necessary to satisfy a female. This makes them sexually incompatible with non dragonmated humans. The humans also gain enough strength to lift 500 kilograms over their heads give or take 100), toughness and endurance to match and heal at about four times as fast as an ordinary human. They also become quite resistant to the breath of dragons.
Dragons were created with a purpose. Planar beings (Demons, spirits, celestials and whatnot) interfered with the world in various ways: trying to conquer it and add it to their domains, warring there with other planar forces, random destruction or slave taking, and etcetera. Dragons live until killed and so do their human mates. The mates learn to ride the dragons and fight with and atop them. The ritual was more powerful than anticipated, though and the dragons became at least as smart as humans, if not smarter. Fortunately for the humans dragons need them to breed. Dragons do not mate directly. When they want to create offspring they size up another dragon with a mate of opposite gender to them and have the humans have sex. The woman becomes pregnant and then lays an egg, which the male dragon will claim as its offspring and raise. The female dragon makes no claim of parenthood.
Dragons are jealous and will not share their mates with another dragon. They have no issues with them fucking around with other humans. If the woman becomes pregnant from a mate of a dragon they donít want in their bloodline then they just eat the egg the woman lays. Sometimes a dragon with no mate will try and steal one from another dragon. This always leads to a death duel. The human ends up the mate of whichever dragon wins.
Dragons are the sentinels and defense against planar beings and they each have their own way of doing it. One may rule a country and militarize it. Another may stealthily hunt and kill dangerous planars like assassins. Some target human cultists that treat with planar beings for powers. The dragon uses itís sizable fortune to equip itís mate and trains him or her to fight.
Ordinary people generally are a bit awestruck and also a bit afraid of dragonmates. Most simply stay out of their way if they can. Those that have to deal with them tend to do so favouring the dragonmate. If a dragon runs the place, of course, then there is less awe but the dragonmate is basically the vice ruler of the land.
I would like to play a human male who becomes a dragonmate. Please take a look at my ons and offs and hopefully at least one of you will want to play this scenario with me.