What I find striking is how flexible the system is - you don't have classes, you have "backgrounds" (a lot like careers in Warhammer), and you can easily write new backgrounds for your campaign/setting. For example, with a day or two of work, you could convert all the Warhammer careers into backgrounds and play Warhammer using Troika! I would argue that it would work just as well, perhaps even better than the original rules - you might have to add a rule or two re insanity, or fate points, and slow down healing, but that's not too hard is it?
So, how would this work for Yoon-Suin? Well I've been running a 5e game with Yoon-Suin for 2 years now, and I've been *thinking* about a GLOG Yoon-Suin game too. 5e works well, but it results in a bit of a "power Yoon-Suin" experience. My PCs are level 8 now, and they have access to potent magic and are kicking ass. It felt like the GLOG (or maybe B/x) would have a more toned down, grubbier, magic is unreliable feeling. Troika! on the other hand would also be more toned down but also more … psychedelic. And shouldn't that tell you which system is the best?
So back to backgrounds and Yoon-Suin. After looking at them, I found that even though they are designed for a different setting entirely, the majority of them work quite well for Yoon Suin (out of 36, maybe half a dozen don't work at all). Intriguingly, some of the ideas/setting elements in those backgrounds really fit well into the setting. For example
- Dwarves are not biological living creatures - they are crafted by other dwarves. This is why Dwarves are not trusted - they are outside the wheel of reincarnation, and thus evade retribution for their misdeed. Each clan of dwarves made each other, and it's why they have their own language. The dwarves are in decline because of the increase of Poorly Made Dwarves (that's a background!), who are warlike but lack any crafting ability (ie are "sterile"). This, incidentally, is a subtle dig at the typical "warrior dwarf" PC that doesn't respect the dwarven craftmenship ethos. I would suspect that slugmen learned some of their Golemology mastery by dissecting dwarves - it is something they would do, is it not? (tangent: check this out to see that idea explored in full).
The dwarves are also genderless/sexless (they don't reproduce right?) so I feel it provides a nice contrast to the hermaphroditic slugmen.
- There is a background who is essentially is a cult that worships bonds, flies and toads. Pissing in the pond is a holy act. This... totally fits in Yoon Suin.
- There are a few "scholar adventurer" backgrounds that are informative, like the Mathmologist. Mathmology sounds like a worthwhile field of study for a slugman
- Members of Miss Kinsey's Dining club. Slugmen can eat almost anything and have refined taste... and are bored. Some will pay large sum for exotic ingredients...
- The Rhino-Man, an other "created" race. I don't think it really adds to the setting, but it wouldn't detract either. I can see these burly mercenaries active in the Hundred Kingdoms.
- Temple Knight of Telak, the SwordBringer. This fits remarkably well with the Bull of Battle. The curved swords are symbols of his Divine Horns. The background gains a bonus to armor based on how many swords are carried (a blessing of the Bull of Battle). They are vigilantly waiting for the end of the world - and what would that end be but the Rise of the Krakens?
- Thinking Engine. This is easily re-skinned to a clockwork golem, but it introduces the notion that some clockwork golems have gone rogue - whatever magical item or incantation that controlled them is long lost. Now they act independently. As the power level of clockwork golems varies a lot, some of them are suitable player character
- Giant of Corda: this doesn't really fit, but there are elements that echoes the Ogre-mage. Using Troika, a "weak" ogre-mage would totally be a playable character
- Yongardy lawer. Trial by combat is not a practice in the Yellow City... but it is in Occidentalia, and it could be in strange lands beyond Xian as well.
The monsters have a few gems too. In general, several of the monsters just... fit so well in the Yoon Suin ethos. They don't change the setting in any way, just add to the flavor. For example, the manticore kidnaps people to be its servants. If hired to rescue a kidnap person, wise rescuers would bring many books, as the manticore love having his servants read to him, and their isolation make finding new literature challenging. You can just drop this in. Undead dwarves are, fittingly, *unfinished* dwarves.
So in conclusion, with a little bit of work, Troika! would work splendidly as a Yoon Suin system.