The Epilogue of Humanity
Lord Leon
SHSL ???

Okay so I came up with a theory that Roxy is Skipper Plumbthroat here.

However, I didn’t know how she’d go about killing the Horrorterrors until now. Rose’s Grimoire has this page which references the part of Problem Sleuth with Fluthlu. The Fenestrated Planes Roxy uses are a direct reference to the Windows in Problem Sleuth, and the link above shows how “cap’n rolal” will be cleaning up the Furthest Ring (to the best of my powers of deduction).