Ferroh has waltzed into my revanchist background notes with a whole b plot (under the cut for three paragraphs of background revanchist ramblings)
he dates Captain Telettoh (the republic liaison guy he shows up with) for the early part of the war (dont know if i want them to get married but if so it would be soon after Malachor). Telettoh later becomes an admiral sometime around Duro, specifically Ferroh's admiral. they start to grow apart during the Sith era (but they still have to work together because admiral and general). right after Telos and the whole Malak jaw incident Telettoh breaks up/divorces Ferroh and deserts; Carth and Morvis and most of the rest left earlier and Telettoh goes to join them with the republic. he's not trusted obviously but he accepts it and does what he can, and the information he brought back is what allows the republic/jedi to stage the ambush that captures Revan.
after Revan gets captured, Ferroh learns of the betrayal and tries to fight Malak/avenge Revan. he loses and dies (unless i want to put Darth Ferroh somewhere in an au. then he leaves and goes into exile). Telettoh hears about Ferroh's death and feels Some Kind of Way about it (not in a good way), and it fully sinks in how much damage his Sith career caused.
not sure how I want Telettoh to die (shot down over Taris just before the Endar Spire crashes? captured and killed? survived and helped destroy the Star Forge? who knows), but he spends the rest of his life (however long that happens to be) trying to undo all the Malak-related damage (and, apparently, warn people about making those mistakes, to the point where he's remembered 2000 years later for saying "Never let Malak aboard" lol)
crucially their relationship does Not work and ends quite explosively (love loses and so do the sith)