Dace asked me to tell you a bit about the Order of Kokujin tattoos, since the family is now available with the release of Great Clans. Mechanically, players should consider tattooed monk and order of the spider monk schools to create characters from this family.
I would go myself for an order of the spider monk 3 then multi school in the tattooed monk : Kokujin didn’t had as much power in his blood neither as much quantities as the Togashi (since he was the only one providing, while they were a couple providing for the Togashi). As such, his students had to prove themselves through his Dark Lotus sect training before being granted any tattoos. In truth, most of the original members of the Order of Kokujin had ranks in other schools before joining and were granted tattoos to enforce loyalty through the Shadowlands power Blood domination but those who joined his Dark Lotus sect (after Kokujin joined with Daigotsu) had to undergo many trials before being granted tattoos.
Now that we cleared the question of which school to use, let’s see about the tattoos in question. I would use quotes from the story The Mad Dragon by Shawn Carman ( http://www.kazenoshiro.com/kazenoshiro/8/h8e02p25.php ) to illustrate the tattoos in question. Those tattoos will have the same mechanical effects, but much darker visual effects. A good thing to throw your players off-balance wondering what those tattoos do !
Matsuo unleashed a devastating cone of frost from his mouth. The cone washed over Kokujin, who disappeared in the blinding sheet of white. The cone gave way to a hissing cloud of steam, however, and Kokujin re-emerged, his body wreathed in red fire, a tattoo of a boiling pit of pitch blazing on his shoulder.
So our first tattoo is the boiling pit of pitch. One of the most visual tattoo ever described, covering the whole body in red fire, his effect is protection. I would use the Crab tattoo, who provide reduction, to simulate this tattoo.
Kokujin's fists grew like stone as the tattoo of obsidian on his back surged with power.
An martial art tattoo, this one can easily be duplicated by the Blaze tattoo.
A Tsuburu no Oni tattoo crawled up Kokujin's back, and the mad monk leaned forward and bellowed. It was a riotous sound, accompanied by a tempest of unbelievably foul-smelling wind. Matsuo was lifted from the ground and dashed against the cavern wall.
An interesting effect for this tattoo : the creation of a cone of wind. Difficult to really imitate that with another tattoo, but you can get it close with the Dragon tattoo. The main difference is going to be in the way damage is dealt (wind instead of fire, which can have different effects regarding to some protection, most likely spells) and the DR of the spell. As a fire-damage tattoo, the Dragon tattoo uses the fire ring. As a wind-damage tattoo, I would use the air ring for the damage rating of this tattoo.
the form of a brilliant white dragon on his chest. The tattoo had not been there only seconds before, and as he rose, Matsuo unleashed a devastating cone of frost from his mouth
Following on my suggestion on making a Dragon tattoo using the air ring, here is a normal Togashi tattoo : the frost dragon tattoo. The Frost Dragon is the wrathful aspect of the fortune Inari, and punishes those who offended him by icing their rice paddies. The Frost Dragon tattoo creates the same effect as the Dragon tattoo, but with frost instead of fire. Using the same basic idea as for the Tsuburu no oni tattoo, the Frost Dragon tattoo would use the water ring for his damage rating instead of fire but works otherwise like the Dragon Tattoo.
Shikibu no Oni tattoo: this tattoo show a representation of the oni lord that stole the bodies of the dead.
A tattoo who isn’t actually described directly in the stories, from the bits of description I assumed it was Shikibu no oni and that the tattoo allowed healing abilities. A dark twist, I would use the Phoenix tattoo to simulate it. The visual of the deadly oni lord moving from one body to another would be quite a scary tattoo.
Here we go, I hope those few lines helped you with ideas about how to turn your Togashi tattoos into scary Kokujin tattoos with little rule changes. There is a lot of possibilities ( Kyoso for Wind, Akuma for Blaze, Yakamo for bamboo…) now open, just take a list of scary shadowlands monsters and you are set to go.