From The Heretic Knowledge Vault
Ms. M is the doyenne -- that's the polite word -- of a family of Tsuirakuans that also includes Kureji Mesuinu, another semi-player character in Errant road who's possibly more familiar from the "Fun with Familiars" omake in Errant Story itself. The Mesuinus are distinguished by three traits: enormous magical power, appalling lack of taste, and gobs and gobs of money, the latter probably a consequence of the former two. Their reputation extends far beyond the floating city; Argus and Lucas both know them all too well, and certain of the other player characters know enough to tremble when the Mesuinu name is mentioned.
The merry band of PC adventurers gets exposed to this remarkable phenomenon when they visit Volkanenborg and Lucas gets word, via Saiko's lieutenant Annika, that the great lady herself has been kidnapped for ransom. A weird quest then follows in the foothills of the Mountains of Madness involving a troll (Grope, who's on the side of the good guys), an elf (Neverinal, who definitely is not), a mage (Sherry) who sort-of-dies and is transformed into a Paedagogusi-like fairy, and all sorts of other fun stuff. It eventually transpires -- spoiler alert -- that Saiko has staged the kidnapping herself, or at least gone along with it, for reasons clear only to the unique Mesuinu mind.
All of this said, while Saiko is definitely warped, she's not really evil ... probably. After the kidnapping caper winds up, she commands a "peace conference" to get all of the rival gangs of Farrel together and ensure that they don't cause too much trouble (a rogue Eisenfaust group being at the heart of the kidnapping) at the Mountain of Madness amusement park, a Mesuinu operation between Volkanenborg and the Mountains of Madness themselves. This leads to further encounters that rope in PC Layla and her family. The Mesuinu magic being what it is, this gets just as weird as the earlier battle.
The play, and the players, have moved away from where this redoubtable woman exerts her influence, and she's not presently adding to the chaos. However, she's still lurking out there, and may be seen again.