Fafnir, Nidhogg, Jormungandr. Such beasts are at the apex of mythology. To hunt and slay a Wyrm (or even to die at the hands of one) could singlehandedly mark someone's name for all of history.
People typically like the idea of more "meteorite type" events, and I think adding epic dragons as a public, contested pve raid/hunt would be a really cool addition to the game. First off, I know haven trends towards lower, mythological fantasy. But I think rare, subterranean threats like a Wyrm could fit right in along the trolls and conch snails if deployed with the "haven monster" art and animations.
The concept i have in mind is a phased dragon hunt, beginning with a server wide message that a dragon has been spotted in the hearthlands.
Phase 1: would be an inclusive, cooperative, server wide hunt where everyone can contribute to finding "Dragon Scents". Dragon Scents would essentially act like a rare crime scent, be visible by anyone regardless of stats, and an arbitrary number of scents would need to be found and used before phase 2 can begin. Each time a scent is found, you would need to bring it to a questgiver nearby in order to contribute to the progress towards phase 2, and you would be rewarded with LP, exp, or a gilding rock/leaf.
Phase 2: once the questgivers have been given a sufficient number of dragon scents, another server message will appear that the nature spirits have divined the location of the fell beasts layer. A new hearthmagic option available to those with druidic rite would become active similar to the star gaze hearth magic, "fell hunt". A new dungeon would spawn somewhere in the overworld, a large cave with a troll's skull belching smoke, the dragon's layer. "Fell hunt" would lead people toward the dungeon similar to a meteor, and, like the meteor, the dungeon would have a "cooldown", period to allow for location and fighting over the structure.
Phase 3: the dungeon itself. The dungeon would follow a similar structure to other dungeons, random rooms, rewards, certain puzzles, etc. these are largely just details, but I think there is room for just about anything! Let me know what your ideas would be for enemies, rewards, puzzles etc. the final boss of course would be the dragon itself, which I think would be fun if it had a randomly generated name each time like other dungeons sometimes do. I have not myself reached the higher echelons of pve content like troll slaying, so it would also be nice to hear from experienced players who have some opinions on how a boss type monster could be made scalable, interesting, and fun. Perhaps there could even be boss phases to run through.
In terms of dungeon rewards, a dragonslayer lore event granting some type of unique passive would be really cool, as would the bones and scales of the dragon itself, perhaps higher quality than anything else.
Let me know what you think. I know it's a more ambitious idea, but its fun just to think about what I would add as enemies and treasures in the lair!