The Big Book Of Spirits

Chapter 5: Special Mention: Spirit Whales

They aren't Spirits, but they are from Spritrelm (a Realm populated almost entirely by Spirits, said to be the birthplace of most Spirit species). They are the only known natural predator of Spirits, and most have an instinctual terror of these beasts (as do Spirikin).

They live in deep valleys between tall mountains, floating quietly along while they wait for their only prey. They are extremely resistant to just about all forms of energy, including magic, and are physically resilient as well. They have three extremely long, prehensile tongues that they shoot out at prey, sprouting hooks to grasp and pull them towards the cavernous mouths of these monsters.

Plants sprout and grow along their backs as they age. They live solely in the Spirit Realm, but occasionally get into other Realms, either by accident or through some evil person's design.

If seen in Mênrelm, it should immediately be reported so the area can be quarantined and a team can be sent out to force the Spirit Whale back to Spritrelm or a special holding facility. Do not engage, especially if you are a Spirit.

Despite the name, they are in no way related to regular whales. No living relative has been discovered, but several used to exist — thank Stars they're now extinct...

They tend to live in familial groups, which can get fairly large. They might seem easy to avoid with their size and large groupings, but often blend in with the floating islands that are common between mountains, luring tired Spirits into trying to land for a rest.