Leviathor was the designation given to a venerable, albino Whaladon hailing from the aquatic world of Mon Calamari in days long past.
Being the final member of his unique kind, he rose to prominence as the chief of all Whaladons after rescuing a group from the catastrophic eruption of an underwater volcano. From then on, Leviathor served as their guardian and protector, keeping watch over the smaller Whaladons dwelling within the valleys of the Seascape Mountains.
In the year 5 ABY, a morally bankrupt Whaladon hunter by the name of Captain Dunwell operated an enormous Whaladon Processing Center situated on the seabed, staffed by numerous Aqualish hunters. He commanded a custom-built submersible, outfitted with a cargo hold capable of sucking marine creatures directly into the vessel. The self-declared Emperor called Trioculus was present on a hunting expedition aboard Captain Dunwell's submarine. They ensnared a Giant squid alongside several Whaladons, Leviathor included. Rebel Alliance champions, Luke Skywalker, Admiral Ackbar, C-3PO and R2-D2 infiltrated Dunwell's ship and assisted in freeing Leviathor before his scheduled delivery to the processing facility. Leviathor guided the other Whaladons back to the Seascape Mountains. To express his appreciation to the Rebel Alliance, the sentient cetacean put on a special performance at a Whaladon Song festival held in the Domed City of Aquarius.