I've been thinking about the concept of dragons for a while, because a) they would be cool, b) they fit fairly well into the mythology of the game and c) because it seems that at least one of the devs has been interested in them before. I didn't feel like resurrecting a half a year old thread, so I made a new one.
OK, so first of all, the issues; They can't be an easily botted resource, they can't just wander around slaughtering noobs and they can't just be a randomly spawning death machine like trolls. I think that they should specifically be OP monsters to challenge the best warriors.
The only think that I've been really focusing on is how and where they spawn, and I've come to the conclusion that the best spot would be mountains, since mountains are meant to be uninhabitable death traps anyway. Pretty much no one lives on them (Wulfs Retreat and a few small hermitages excluded) and the only reason for anyone to go there is for the natural resources, snow or to hunt mammoths. In short, I think that most people wouldn't be too bothered if a dragon spawned on a mountain, unless they are part of a faction that gathers the natural resources there, in which case their faction should be strong enough to challenge the dragon.
As for how they spawn, I had an idea at the end of last world, with the info box that tells everyone about the Altar of Ruin when it appears. I think that very rarely, throughout the duration of the world, a dragon should spawn on a random mountain. This should only happen maybe once every month or two. The dragon will have an territory around where it spawns, which ends at the edge of the mountain or a certain distance from the initial spawning area. It will instantly attack any player that enters this area or any player that attempts to attack the dragon from outside its territory. Also, to warn everyone of the threat, a lore should activate for everyone who logs into a character in this time and another will activate when the player approaches the edge of the dragons territory. Also, if someone tries to lure the dragon too far from its territory, it will take flight and respawn back at its territory with full health. Also, it will destroy any buildings within its territory. What does everyone think?
PS I know that I haven't said anything about the dragons abilities or how their strength should be scaled, but I don't fight much so I don't really understand the combat system or know how to balance combat, so I wouldn't have any decent ideas.