The players in my saga wanted to do some research into legendary dragons, so I prepared a handout as a result of their efforts (after some Magic Lore rolls and off-screen research). I thought I'd share what I compiled (it's translated from Swedish but I tried to make it look good after a GPT run).
It was really for story reasons (and where I figured I could take the saga if they ran the pipe). Basically they figured that an option to "restart" the regio of Muspelheim they needed potent magical fire of some sort (and dragon fire was one option of many fun mythical options or they needed a calculated 15+ magnitude CrIg effect). The lava fires (and fire giants, including Surtr) had died out due to their action of sending the winter-kings powerful possessed knights there. Bad idea, which also screwed up their magical aura (as Muspelheim is one of 9 worlds feeding a vim-flow of magic in my saga, no more Ignem boost in the covenant or forest area!). Very long story (and fun) for another time.
Anyway, the handout below (translated). The dragons chosen are combined from real myth and Ars supplements and I selected what the characters actually knew about them (darn good Magic Lore roll, and the player has specialty beasts of legend...)
Would be happy to hear about additional legendary dragons (from RAW, myth or your sagas).
Legendary Dragons
Leviathan Kete
In the realm of Aethiopia, Queen Cassiopeia's claim that she and her daughter Andromeda surpass all of Poseidon's Nereids in beauty provokes the god's wrath. He unleashes the dragon Kete, commanding it to ravage the kingdom's shores and harbors. The Oracle of Ammon decrees that only by sacrificing Andromeda to the beast can relief be found. Thus, she is bound naked to a seaside rock. Perseus, the valiant hero, slays the beast and claims Andromeda in marriage. Tales of the Leviathan persist even after its defeat by Perseus. Rumors swirl that Kete still haunts the Red Sea and the Eastern Mediterranean, whimsically flying between the two, tormenting local sailors with fear and superstition.
Pan Caudarax
Around a millennium ago, the dragon Pan Caudarax left Flanders for "The Island," abandoning a legendary treasure, including the Rosewood Crown, a divination tool for oracles. It vowed to return on the day of the Crescent Sun to defend its treasure against the legendary Sorcerer De Panne.
The Golden Serpent Impathis
In the 5th and 6th centuries, the dragon Impathis, known as the Golden Serpent for her splendid golden scales, ravaged cities and kingdoms around the Alps in her ceaseless quest for gold and gems. Many brave knights sought to slay her but never returned. Eventually, Impathis retreated to a hidden location in the Alps and has not been seen since the 7th century. Only mad mundane knights still search for her, lured by tales of her immense treasure and reputed wisdom. She was known to converse with scholars, blending wisdom with avarice.
The Dragons of Mont Pilatus
Mont Pilatus, a majestic mountain near Lucerne in Switzerland, is steeped in dragon lore. These beings, more than mere beasts, are shrouded in magic and mystique. Dwelling in the fog-enshrouded caves and deep chasms, they exhibit power and majesty, with scales shimmering in every conceivable hue and vast wings that stir the clouds and echo through the mountains. These dragons wield control over weather and winds, with breath either icy cold or scorchingly hot. They are revered as guardians of wisdom, with eyes glittering with ancient knowledge. Their scales' morning dew is sought for its magical healing properties. However, these dragons can also be perilous, particularly when their domain is encroached upon. Many have sought to challenge them, often meeting grim fates.
Fafnir
In the 5th century, Siegfried, a knight from Xanten, hears of Kriemhild's unmatched beauty and seeks her hand. He first claims a vast treasure from the Nibelungs by slaying them and taking the Tarnkappe from their dwarf treasurer, Alberich, becoming ruler of Nibelung's land. Siegfried slays the dragon Fafnir in Westerwald, bathing in its blood, rendering his body invulnerable except for a spot on his back. He aids King Gunther in winning Brünhild's hand by deceit, stealing her ring and girdle for Kriemhild. This tale culminates in tragedy and the Nibelung's treasure remains lost, allegedly sunk in the Rhine by the traitor Hagen.
Nameless Scandinavian Dragon
In 6th century Ultima Thule, Beowulf, endowed with the strength of thirty men, slays Grendel in King Hrothgar's hall Heorot. Later, as king, he faces a dragon awakened by a thief in a cave. With only his kin Wiglaf's aid, Beowulf confronts the dragon, but ultimately succumbs to his wounds. He is honored posthumously with a sea-visible burial mound in Götaland [land of the Goths, southeast Sweden]. The dragon's fate and resting place remain a mystery, with few clues to Beowulf's grave.
Ladon
Trianoma, of House Bonisagus, is said to have located Bonisagus by heeding advice from Ladon, guardian of the Hesperides' golden apples. Others speculate she used magical coordinates from remnants of Ptolemy's lost "Geography." The dragon, deemed invincible and ever-vigilant, might still exist.
The Wawel Dragon
This dragon, residing under Kraków's Wawel Hill, terrorized the region until outwitted by a cobbler's apprentice, who fed it a sulfur-laden sheepskin, leading to its demise.
Unknown Dragon on Isle of Man
In 1160, a powerful dragon destroyed the nascent covenant Servus Maris on the Isle of Man, sparing only one magus to warn others. The dragon's affiliation remains unclear, with speculation about Diedne, the Scandinavian Odin's Order, or another power.
Unknown Dragon on Iceland
In 1224, a Loch Leglean magus investigating ghostly occurrences on a Scottish island learns they stem from Hadrianus of House Flambeau, slain a decade prior while probing Odin's Order rumors in Iceland. Hadrianus' spirit speaks of a formidable dragon summoned by the Order before finding rest. This incident stirs calls for revenge and action against Odin's Order.