Typically a progression style deck associated with a particular quest includes all cards released to the point of that quest. For something like The Black Serpent, this doesn't mean a lot at this point in time, since only Mountain of Fire came out after it.
However, I thought to myself that a different spin might be interesting -- instead of drawing from the card pool to that point, how about including at least one of every card released in The Black Serpent? I'd need a two-deck fellowship to cover all four spheres, but could I come up with something that makes sense?
The first step was to pick the heroes. Fastred had to be chosen, so I picked Dunhere as the obvious combo with him. Since the pack has Southron Refugee, that meant Kahliel as a third.
The next piece of the puzzle was Fearless Scout, one of the most useless attachments in the entire card base. What earthly good is it, since Warden of Arnor is the only scout-related attachments and isn't so powerful that you'd want Fearless Scout just to play it? The answer has to be with Scouting Party -- I need Fearless Scout so that I can play Scouting Party and keep a strong questing hero in the mix. Khaliel's a possibility for it, since he can be buffed by headdress and his kinsmen, but what are the other non-spirit (already have two) scouting heroes?
Leadership: Elfhelm
Lore: Haldir, Argalad
Tactics: Hirgon.
Elfhelm and Hirgon were easy choices, decent questers with (in Hirgon's case) a questing related ability. Plus they combine to allow Oath of Eorl to be played, and Elfhelm encourages song/mount mixtures that would help with Burst Into Song. Hirgon also makes playing Defender of Cair Andros cheaper, and his threat-raising can make it more powerful.
Haldir and Argalad both can mix well with Dunhere/Fastred in different ways, but neither are questers (at least without Light of Valinor). But the real problem is the two remaining cards from the pack, Old Toby and Dunedain Pipe. Dunedain Pipe would be really useful with a Dunedain hero (Beravor, Aragorn, Thurindir are the choices in Lore, and Thurindir also could fetch the side quest), but for Old Toby I want lots of pipes, and I decided my final hero would be Lore Pippin. With the low threat of the Fastred deck, I can theoretically engage, dump to staging and kill while getting a card and lower threat out of it. I can put a hobbit pipe on him and a hobbit pony and do elevenses shenanigans, and use Bilbo ally to put another hobbit in play. And best of all I can justify Fearless Scout on him by buffing up his willpower to insane levels with Rosie Cotton and mixing Fireside Song with Song of Travel, Song of Hope, Song of Earendil....
I still need a Dunedain Pipe, so I need a Dunedain character, preferably a questing scout. Sulien immediately sprang to mind, but since it doesn't have to be on a unique character there's a lot of good choices -- dang it, I should've included more than one copy!
I also wanted to use Dwarf Pipe, to do Old Toby proper justice. That's only useful when discarding, and since I have no dwarf heroes for King Under the Mountain, that means Zigil Miner.
So with all these things going on, I didn't manage to stay at 50 cards or even close -- but I do at least have something that pretends to be a viable fellowship here:
http://ringsdb.com/fellowship/view/3528/the-black-serpent-fellowship
I haven't actually tried it yet, and I expect The Black Serpent will crush it. However, it at least is a fellowship where all the cards from the pack have a purpose, even if it'd be stronger without some of them.