The last of his particular species, he became the leader of all other Whaladons by saving a herd from the deadly overflow of an undersea volcano. Since that time, Leviathor acted as their guardian-protector, watching over the smaller Whaladons in the valleys of the Seascape Mountains.
In 5 ABY, an unscrupulous Whaladon hunter named Captain Dunwell maintained a massive Whaladon Processing Center on the ocean floor, manned by dozens of Aqualish hunters. He piloted a specially designed submersible, equipped with a cargo bay that could vacuum sea-life directly into the ship. The self-appointed Emperor known as Trioculus attended a hunting trip aboard Captain Dunwell's submarine. They captured a Giant squid and several Whaladons, including Leviathor. Rebel Alliance heroes, Luke Skywalker, Admiral Ackbar, C-3PO and R2-D2 boarded Dunwell's ship and helped to extradite Leviathor before he could be delivered to the processing center. Leviathor herded the other Whaladons back to the Seascape Mountains. To show his gratitude to the Rebel Alliance, the intelligent mammal performed a special concert at a Whaladon Song celebration in the Domed City of Aquarius.
- The Glove of Darth Vader (First appearance)