How does this work? Am I just attempting to be cool-by-association?
1) Any "legitimate" PC is welcome to play in a Fortress Eibon game (barring situations such huge level discrepancies between characters).
Your AD&D PC from your childhood campaign in the 80s? The welcome mat is out.
A PC from another current D&D game? Of course! Just keep it on the down low if your DM is a stick-in-the mud...
A PC from another edition of D&D? Chances are that the PC would be converted to a more orthodox character class for their Fortress Eibon follies, but come on in! (Just please don't whine about not having feats). For fancy-pants such as Monks, Illusionists, Paladins and Rangers I'd probably use the rules from OD&D/The Strategic Review or the Labyrinth Lord Advanced Edition Companion (with a bias-towards OD&D versions). But pretty much any non-insane oldschool character class is legit (i.e no UA Barbarians or Cavaliers please!).
A PC from another RPG system such as GURPS, Rolemaster, Tunnels & Trolls, Traveller, Villains & Vigilantes or Call of Cthulhu? Yep, as long as you're okay with my interpretation of their D&D incarnation. (CoC characters adventuring in Fortress Eibon? Sounds like those investigators are having a Dreamlands escapade).
This came up when I found a stack of old lost 3.5 and 4E character sheets for the players in group in my office, "Whoah! There's a whole lotta Fortress Eibon fodder here!"
2) Your PCs are welcome to buy goods offered for sale in the Flailsnails marketplace such as kickass Erol Otus armor. or Everburning Torches of Dundagel. (I wonder if any enterprising Flailsnails PCs will set themselves up as trans-mileu merchants?)
3) You are welcome to run your Fortress Eibon PC in other DMs' dungeons, games and campaigns. You own them, not I.
Let the Dragonborn and