From Ryzom Wiki
Here is the tale of the Ghost Yubo.
Long, long, long ago in the Old Lands, yubos were not as weak as they are now. They were little (and sometimes not so little) balls of fury if you angered them. Their urine was so potent it could eat holes in your boots.
But they were not so strong that they could not be brought down by homins and used for food and the crafting of useful items.
But as years went on the yubos became weaker. Over time homins only used them for target practice and did not bother to quarter the bodies for materials as they had before and the yubo bodies were left to rot.
One season during Anlor Winn, the evil wind blew upon a dying yubo and filled it with malevolent purpose. The yubo rose up as bones and he fled to where the wind issued from the spirit world and entered there.
The next time the Anlor Winn blew, the little Ghost Yubo came back into the world. As it wandered the bark, it took flesh from the corpses of slain yubos and grew stronger, then returned to the spirit world.
Each Anlor Winn the Ghost Yubo would return to add more flesh to its bones. Over time the Ghost Yubo grew stronger and stronger, and larger and larger, but the bones still showed through the flesh it took.
Finally its power grew so great that it could make other yubos look like itself when the Anlor Winn blew. You have all seen this, no?
Sometimes it sends minions, little copies of itself, out to gather other yubos and bring them to the Ghost Yubo, who will absorb them into its being so that it can grow ever larger.
Sometimes these minions will attack other creatures as well, even homins!
In the season of Anlor Winn, beware of yubos! The Ghost Yubo is out there… waiting.
— as told by an Old Tryker during Anlor Winn Story Tales in the 3rd CA of 2575.