Elephants crossing the seas!
It is not an infectious disease, but it is a plague upon the world.
For it spawns villains. And not your garden variety villains, but epic villains, master villains of the most dangerous kind Evil Geniuses.
Pnathic sorcery has existed for ages, crudely used by magi who no idea the true forces they were fumbling with.
An article concerning the nature and role of druids in an RPG enviroment.
Plagues and other great diseases are important parts of history and some settings. They defy man and may even defy God in their swift and terrible punishment upon the body of society.
Expansion from the Horse Brass item: Specific Armor charms.
Cooling Touch Charm: protects horse against extreme heat, and fire, magical and mundane
Jove's Favor: tin charm shaped by a lightning bolt that protects a horse primarily from natural lightning, but also potentially from lightning based attacks. In real life, lightning kills quite a few horses and cattle a year.
Hermes' Blessing: gold charm that grants the horse magic resistance, and perhaps immunity to cantrip level magics.
Vulcan's Steed: This large iron charm in epic fashion renders the steed invulnerable to iron weapons. Such things clatter off of the animal's hide like twigs.