Rhaknam (モビス Mobisu) is a huge arcwhale that roamed the skies, always shrouded in a thick fog.
Rhaknam is known to accidentally destroy ships, causing it to become the nemesis of Drachma when Rhaknam destroys Drachma's first ship and kills his entire crew, including his son, and robs Drachma of his right arm and eye. Ever since, Drachma went after Rhaknam to avenge his son and his crew, until the middle of the game.
Whilst flying around Valua, Rhaknam is attacked by Ramirez's fleet until the Little Jack intervenes. Drachma is successful in firing the Harpoon Cannon into Rhaknam, but the distraction allowed Ramirez's ship to get behind the ship and open fire. With the Harpoon Cannon still embedded in it, Rhaknam dragged Drachma and the Little Jack with it back to its home in the inner ruins of Glacia (a move which ironically saved Drachma's life).
It is later when the party is reunited with Drachma that Rhaknam is revealed to be the Purple Gigas, Plergoth (パプニール Papunīru). Fina stated that the Purple Civilization implanted the Purple Moon Crystal in an average arcwhale, creating Rhaknam. After the Purple Civilization perished (presumably in the Rains of Destruction), the Gigas was left to roam the skies ever since.
However, Ramirez's attack on Rhaknam left it fatally wounded. Feeling indebted for saving his life, Drachma made peace with the arcwhale and stayed with it during its final moments. Rhaknam eventually dies from its wounds, releasing the Purple Moon Crystal in the process.
- Rhaknam is based on the titular whale from the 1851 novel, Moby-Dick, a reference further supported by its Japanese name, Mobys. Its Gigas name in Japanese, Papunīru, is likely a portmanteau of the Japanese word for purple and Fafnir, the name of a dragon slain by Sigurd in Norse mythology.
- No evidence from the story supports why Drachma refers to the Purple Gigas as "Rhaknam", though it's likely that after the Purple Civilization was eradicated its true name was lost to all but the Silvites and the name Rhaknam was adopted by sailors who encountered the wandering Gigas.
- Rhaknam's death was nominated for Most Memorable Moment in the 2003 Nintendo Power Awards. However, it lost the award to The Legend of Zelda: The Wind Waker.
- Rhaknam has a cameo in Sonic and All Stars Racing Transformed in the Skies of Arcadia track, where he travels under the islands.
- Rhaknam is also the only Gigas who doesn't seem to directly oppose Vyse and his crew, possibly because he managed to retain some of his animal characteristics after he was implanted with the Moon Crystal.