So I’m making my own fake Pokemon region, Unotos, and in it I’ve got gremlin Pokemon. I know I want them to be Fairy-type, but what should be the secondary type (if any)? I mean, Dark seems apropos, but Flying is closer to the gremlins’ origins but not in the “correct” way. Maybe a Fairy/Dark line with an ability that makes their moves super effective against Flying and Steel-types as gremlins in folklore sabotaged aircraft? I respect your opinion immensely and would love your advice on this. :)

I like the idea; it’s a good excuse to have a Fairy Pokémon on the more malicious side.  I agree that Fairy/Flying isn’t quite right because gremlins don’t (I think) actually fly in spite of being traditionally associated with aircraft, and Fairy/Dark seems to make the most sense immediately – but then hey, who says your gremlin Pokémon can’t have wings after evolving (or just be able to learn Fly)?  I think that would also make a great deal of sense, and be a good way of playing with the basic concept.  As for beating Steel-types, what jumps to my mind would be a “Sabotage” attack – Fairy-type (physical?) but super-effective against Steel Pokémon in the same way as Aurorus’ Freeze Dry beats Water-types.  As for an ability… Technician seems like the logical choice (bonus points if Sabotage has 60 power and can get a Technician boost).