I saw Death coming toward on a cat as pale as moonlight. It lunged through the night with such an expression of ferocity I thought it would rip my throat out. But as it reached the battlefield, Death struck it with his glittering whip. He dismounted, and the cat fell to the ground, for nothing that touches Death survives.
--diary of a soldier
There are many myths about spirit cats--most, like this one speak of a moon-white cat which Death rides as he goes in search of souls. Some believe there is only one cat, while others say he breeds them. They are said to walk between the world of the living and the world of the dead and to be nearly as ferocious as Death himself, with a hunger for blood that cannot be satiated. Scientists have found no evidence that such animals exist, but believe that the myths may have arisen from the white jaguars that live along the Drea'im River. Ironically, these cats have been found to be more docile than most wildcats, and have actually developed a tentative relationship with the people who live in the jungle. As usual, science doesn't have it quite right.
From what I can glean, a group of Ghost Speakers learned how to trap a spirit not only in an object, but in the body of an animal. They chose the white jaguars for their size and power. For once the spirit was trapped inside, the jaguar would try to escape it by running, and thus the Ghost Speakers could travel great distances astride the jaguars, and remove the spirit when they wanted to stop. Many of the white jaguars were killed this way. Due to their habitat being along a river, the Tenganaw considered them sisters, and vowed to defend the white jaguars, promising to slaughter anyone who dared to hurt them. The descendants of these people still live along the Drea'im River, though most believe that the monsters that once possessed the white jaguars are long dead.
When a soul is trapped inside a jaguar, it's primary thought it to escape. which usually results in it running, in an attempt to flee what frightens it. The instinct to run overrides all other instincts, and if the soul is not removed quickly, the jaguar will run itself to death.
Perception and Sensory Capabilities
Most Ghost Speakers believe that when a jaguar has a soul trapped inside it, its senses are heightened, but this also heightens its level of fear, and some have been known to die of fear while the rider is upon them.