From Introduction:
Most people who encounter a Griffarcus up close see one only as the steed of some veteran adventurer or a powerful mage. Little do they realize the dangers such a steed presents. The Griffarcus is a traveller between worlds, wandering from plan to plane, able to grow and shrink in size. Perhaps its most important characteristic, however, is that its tail can transform into a venomous snake at a moment's notice. Those who wish to tame a wild Griffarcus and make it their steed must use magical spells to counter this attack, or they will quickly find themselves walking through Death's dark gate.
On the surface, a Griffarcus seems to have the body of a llama or an alpaca, but its head is more like that of an anteater, and it has white, feathery wings with which it can fly short distances. They normally travel in small herds, though it is not unknown for planeswalkers to encounter an ancient, hoary Griffarcus all by its lonesome. These loners are usually more dangerous than herds, however, being unafraid to attack those who oppose their wanderings.
The Griffarcus, being an omnivore, eats vegetation, any kind of small animal that is slow enough to be caught, and whatever carrion or garbage that is left behind by others. Perhaps because it travels so widely across dimensional boundaries, the Griffarcus is highly resistant to poisons, toxins, and other food impurities.
If you can find the spell that wizards and adventurers use to tame, them, maybe you can make one your own steed. But do not expect someone else to sell you one, for the Griffarcus is literally priceless — the spell only protects its caster from the venomous bite of its serpentine tail.