One of the most fearsome beasts that dwell in the fell land of Corpsefall, these creatures bare a resemblance to the noble lion. Though when once considers the scale of these creatures, one can overlook these similarities.
The Leonomuth appears an immense lion, though with a stockier build. They are fully 20' at the shoulder and near as broad. Where a lion would have a mane of hair, the beast has long, porcupine-like quills that can reach lengths of 4-6 feet and an inch in diameter. In place of fur, they have scales like a crocodile, though of a golden hue. Their teeth no longer form the distinctive paired fangs used by terrestrial lions to kill prey, but instead their teeth have fused into a serrated ridge for carving out huge gibbets of flesh. The claws of the Leonomoth are not as formidable as their jaws, being thick, non-retractable and relatively dull. They still have the power of a many-ton creature behind them, so they are still lethal to smaller creatures.
A Leonomuth readily joins the feeding frenzy that follows a recent corpsefall, but does so first to devour incoming scavengers. It is fierce enough and quick enough - despite its size - to snatch up Griz, Devourers and even smaller Boneslugs. They seem to prefer this prey to the corpsefalls, but once all available scavengers have been eaten or driven off, will settle down to work off the carcass.
Leonomuth's are no more intelligent than terrestrial lions, and do not form prides. Female Leonomuths are as large as males, differing only in their absence of the spiny mane. Mating is rare and dangerous, and the battles between males for females are epic, the clashes occasionally bringing unfortunate scavengers that thought them a corpsefall.
Leonomuths are occasionally summoned by magic from Corpsefall, virtually always as agents of destruction. Their immense appetite dooms them on most worlds, for few places can provide them with the amount of meat they need to live. They will not cross water they cannot leap across, so this greatly reduces how much damage they can inflict.
The Leonomuth is a monster, pure and simple. On its home realm, it is a hazard somewhat greater than all but the largest Boneslugs. On other realms it is a heroic challenge to be bested by the strong, or worn down by an army. One could serve as a mount for some great demon, demi-god, or perhaps even a Giant.
Additional Ideas (2)
The poison also loses its efficacy after 1-3 days, and so it is impractical to store it. The only people who will bother poisoning their weapons are people who own a leonamuth. And when you own a leonamuth, you have a better ways to kill people than with a poisoned lance.
Leonamuths build elaborate dens. Their spines constantly grow and fall out. Discarded spines are carried back to its den and stuck into the ground, pointy end up. Larger, more practiced lions might even weave them together, to make something like palisade walls. Given enough time, this can resemble a (very small) labyrinth. There are rumors of a family of leonamuths that live together, and that have spent the last few centuries building a tremendous structure of woven spines. It is a honeycombed maze, and a familial den for the beasts. If anyone has ever found it, they have probably not survived to tell the story, so most disbelieve this "myth".
Leonamuth also use their spines to store leftovers, on the rare occasions when they are unable to finish a meal. Meat is gathered by rolling around in it. It is retrieved by shaking, like a wet dog.
Leonamuth spines are rarely made into permanent weapons, simply because they become brittle once they dry out. However, they have a famous and permanent usage in the Bone City, where they are used as dueling instruments. They have exactly the proper strength and flexibility to be used as dueling foils. The duels are always fatal and usually brief--one good poke with a fresh spine and you have only a few seconds left to poke your opponent before your brain turns to vinegar and your bones to sand.
Male leonamuth are very territorial. Although they will "adopt" a previous male's den if they take over the territory, they will also sabotage and destroy another male's den when given the chance. For smaller males, this is the only weapon they have against larger males.
Leonamuth will sometimes howl together, as regular as clockwork. They do not howl in response to any visible stimuli, but most sages will tell you that they howl in the direction of the next big corpsefall.
And for higher level PCs: http://en.wikipedia.org/wiki/Champawat_Tiger
Built according to instinctual blueprints, spine-dens always work to funnel and amplify sounds towards the center. A listener in the center of the den can hear noises coming from ten times farther away than they would otherwise. Bigger dens are more powerful amplifiers, and the most successful dens are built on hills (although in flat areas without any tree cover, elevation doesn't matter).
For this reason, it is nearly impossible to sneak up on a leonamuth in its den. If you stumble upon a leonamuth's den, you can be assured that it is not home, or else it would have heard you coming and killed you by now.