The Luminous Krayfin, also often refered as the Leviathan is a non-playable, Tidal class dragon released with the The Secret of Leviathan expansion on March 2nd, 2017.
As for v2.7.0, the Titan/Adult Krayfin will swim in cycles in Impossible Island.
According to The Bork Papers (found in the first mission of The Secret of Leviathan Expansion Pack):
- "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."
*= In-game typo.
To learn more about the Luminous Krayfin, go here.