I'm going with it just being different mystical traditions than elsewhere in the world. Dunno if that's fully canon, but then there almost isn't any anyhow.
The only thing we really know about canon Cathayan magic is the following due to how little GW focused on that region:
Cathayan Magic
Magic has a long history among the
humans of Cathay. In their tradition,
Dark Magic and
High Magic (known as yin and yang, respectively) are both held as sacred energies. Sometimes Cathayans use
jet to craft fine pendants, bowls, rings or other trinkets that serve as protective amulets against all forms of hostile magic, excepting for those two and, for some reason,
Ogre Gut Magic.
[10g]
The strongest school of magic appears to be
Astromancy -
Dragon Emperor Xen Huong had a coven of astromancers already circa -2750 IC, and they were so powerful that some credit them with the summoning of the
warpstonemeteor that crashed in the Ogre homelands and created the
Great Maw.
[10a][16d][17a] Celestial Magic is still important in the Empire of the Celestial Dragon, as the Tower of Ashshair kept watch for signs and portents of woe and threats from distant lands, and when it was attacked by
Sayl the Faithless around 2509, his vanguard forces were crushed under a comet brought down by magical means.
[18b]
Another magical feat of this great empire was the overturning and sinking of the
Dark Elf Black Ark Talon of Agony in 860 with a gigantic magical tidal wave off the coast of Cathay.
[4b]
Some, if not all, Cathayan wizards are known as Shugengan, and are said to have
Dragon blood in their veins. They are able to hurl blasts of white fire and blizzards of murderous ice-shards against their foes.
[18b]
Clan Eshin also learnt from Cathayan sorcerers and certain groups in Nippon, blending what they already knew of the warp with the techniques used in Cathay to develop their own lore, one that serves to enhance their Clan's power and mystique - the Lore of Stealth. These spells are designed to augment the stealth, speed, and strength of the Clan's attack forces, and none are quite sure whether Clan Eshin
Skaven's legendary skills have ever been completely mundane. Clan Eshin guards the secrets of this art to ensure that none of the rival Clans learn the answer. For this reason, Eshin Sorcerers are mysterious, rare, and keep to themselves; they are well aware that the
Grey Seers brook no competition from other Skaven spellcasters.
[20g][20j]
Tzeentch's crew apparently had a foothold in Cathay via a cult that worshipped him as Chi-an. They were rivals with a group of vampires called the Jade blooded.
Tamurkhan: Throne of Chaos, a book from
Forge World's fantasy line, quite surprisingly contains a battle scene where the forces of Cathay are involved. A chaos sorcerer dupes a Beastman army into attacking the Tower of Ashshair, a Cathayan watchtower outpost at the edge of the
Ogre Kingdomswhich it uses to scry on the Old World. Its defenders included fancy bronze cannon that shoot harpoons, "crow-men", stone "temple dogs", elite warriors with back-banners and "thousand-folded" swords, and "Dragon-blooded Shugengan" who wield elemental magics. In other words, your usual collection of oriental cliches,
mostly Japanese. And sadly, it's likely the closest thing we'll get to an official Cathay army list.
But then, things get interesting when the Tower's garrison started to get overwhelmed by the
Beastmen's numbers. The Tower turns the tide by dropping a frikking'
Comet of Casandora into the horde, then starts sending "strange creatures of living stone" that can swim through the ground, bronze golems, terra-cotta soldiers and minotaur-suplexing "living statues of onyx" to beat the shit out of the survivors. So at least we know that Cathay isn't to be messed with in the Warhammer world.
Also the name of the native spellcasters
Shugengan seem to be derived from the shugenja, the 7th century practitioners of the Japanese religion of Shugendō. They were sometimes known as yamabushi too.
We know even less about Nippon magic just that they worshipped a common deity with Cathay the Orange Simca, whose monks exist in both places and wear orange robes and spend most of their time in contemplation which gave them special powers. Vimto is the martial version of Simcism.[2b]
The stone statues known as Temple Dogs can be found in both places guarding temple entrances. They resemble nothing so much as a cross between a giant pekinese and a lion. In times of war, the power of the temple gods is channeled into these statues to animate them. It is a great honour to mount this divine animal, indicating that the rider has found great favour with the gods.[4a]
Some Nipponese worship Lord Tsien-Tsin, known in the Old World as Tzeentch.[9b]
