- "The Luminous Krayfin thrives in a humid habitat and must feed on the Dragon Bloom, a most dangerous flower. Only then can it become a leviathan. Extremely dangerous. Pray you never see this monster on the seas."
- ―Bork Papers-School of Dragons
The Luminous Krayfin is a large Tidal class dragon that made its first appearance in the School of Dragons expansion "Secret of the Leviathan". As an adult, it becomes a Class 10 Leviathan, just like the Bewilderbeast.
The egg of the Krayfin was previously referred to as the "Mysterious Blue Orb". It is a large round egg that is a glowing cyan blue in color with darker blue swirls around its circumference.
The "Mysterious Blue Orb" was first seen in the School of Dragons Expansion "Battle for the Edge". In this expansion, the Dragon Hunters first had it, and later Harald Forkbeard steals it from the Hunters. At this time, the player is not sure what the Orb is.
The "Mysterious Blue Orb" reappears in the next School of Dragons expansion: "Return to Dragon Island". Through various quests, the player and the Dragon Riders gain control of the Orb, which the player realizes is an egg. The expansion ends with the egg hatching and Hiccup saying his famous line, "This changes everything". The following expansion, "Secret of the Leviathan", reveals that the egg has hatched into the Luminous Krayfin.
Hatchling and ShortWing
The Hatchling and Shortwing growth stages of the Krayfin are seen in School of Dragon's expansion, "Secret of the Leviathan". It has four short legs, each ending in a long flipper, and long wings. It is capable of long flight at this age. Its body is rotund and has a chunky short-snouted head. It has a line of luminescent spots trailing along its body. Depending on the lighting within the game, the Krayfin appears to be indigo or dark blue, gray at other times, and even dark green.
According to Hiccup, the Luminous Krayfin grows rapidly.
Adult and Leviathan Stage
These growth stages are unknown yet. However, the "Bork Papers" reveal that in order for the Krayfin to become a Leviathan (Tidal Class Titan Wing), it needs to eat a plant called the Dragon Bloom. The dragon bloom produces a special fruit that increases the growth speed of the Krayfin.
By the end of the expansion, the Krayfin has grown tremendously, but the player does not know if this is an adult size or still a larger juvenile size.
- The Luminous Krayfin is the first Franchise dragon to start with the letter "L".
- The Lycanwing also starts with an "L", but it is unknown if it truly exists
- The term Leviathan seems to be more of a classification based on the sizes of Tidal Class dragons, not to be confused with the actual name of the dragon itself.
- This dragon is not a rideable dragon at this point in the game. However, if you leave and return to Impossible Island you will see it swimming in the lagoon at the bottom and if you time a jump from the bridge just right you will land on his back and not be forced to respawn on the bridge.
- The adult form of the Luminous Krayfin resembles a combination of a seal, a sea turtle, and an alligator snapping turtle.
- According to the pictures in the Bork Papers, this dragon's jagged, rocky back is powerful enough to completely break a Viking ship in half.