Seireigi is a game that was initially conceived from wanting to make a game that could be played with a single standard Chess set while also reducing the importance of material advantages. Although such a game never came to fruition, I was able to do the next best thing, a variant of Shogi with promotable Gold Generals, as well as more varied and animalistic promotions.
Note: the source page for the Rules tab is the Chess Variant Pages article on Seireigi, which hasn't been officially approved yet. Until it is approved, only members of the Chess Variant Pages can view it. However, there is a preset for Seireigi on Game Courier (the site's PBM service for Chess variants), which you can use to fact-check the rules if need be. You can find the Seireigi GC preset here.
Note: the source page for the Rules tab is the Chess Variant Pages article on Seireigi, which hasn't been officially approved yet. Until it is approved, only members of the Chess Variant Pages can view it. However, there is a preset for Seireigi on Game Courier (the site's PBM service for Chess variants), which you can use to fact-check the rules if need be. You can find the Seireigi GC preset here.