Give them a passing mention at the least. If a storyline doesn't tie-up all major characters (major character- one who plays an active role in making the story end the way it did) then the novel falls flat in my opinion. You walk away wondering what if, and I'm not too fond of that. You don't have to mention every minor character that dies, but do take the time to give us a general sense of what happened.

I don't know how major a role all these plotlines play in your story, but, like Rosey said, passing mentions throughout is the way to go if these plotlines are not central to your story. I would avoid the epilogue thing, at all costs, personally. Tying everything up into a neat little bow in the epilogue is no fun. Also, if these are just minor characters that we meet in passing, I really don't think their fates need to be laid out. If they have played a significant part in the story, sure, mentions and maybe even more appearances may be in order. But I think that a few minor characters who showed up maybe once or twice can be left hanging.

If these plotlines are hugely important and you have a whole slew of main characters, you might want to try and weave them into future events. Just make sure you don't veer off the path of the main story, or things get nasty and complicated.

Things are already complicated Writersdomain. Since the story follows soldiers on both sides going into war I have them split into 3 and 4 plot lines a piece, with each respected side having a Northern, Central, Southern front. Plus those caught in the middle of the war.

Most of them are about as main characters as you can get. They are critical in every scene and are related to each other because as they ascend, a few make a name for themselves in the military. I'll try to give them each a piece, since they are not really minor characters.

Or, option two is to end in a way that gives a nation's fate. I read one book, I Am Apache, that ends in such a way you know the fate of all characters. Even though it's just the MC saying what she will do, what she does applies to her whole nation. You could pick one character and have him say the fate of one front, another character for another front, and so on. Might make it less messy.

Yes, Rosey, that is exactly what I did with one of the surviving characters. He becomes a General and reflects on great heroes of the battles. Few of the characters ever meet face to face between the 7 plot lines, but each character and their closest friends has their own stories.

I originally wanted something like Band of Brothers crossed with War Stories. Or perhaps Battle 360 with 'Lucky E' in which the characters who participated each gave a unique look into history altering battles.

There are no big dramatic monologues or final words because they already HAD their final words. Each and every soldier considers himself dead. They have written their wills, said their goodbyes and quite literally marked their own graves. The concept of a Living Funeral exists in my world because of how lethal conflict it. Soldiers are never to return to civilian life, even if they survive a war or battle.

Endings are just as hard as the beginnings!

Fewer characters, Jen. That's the secret.

In "Warriors" for example, there is one main character: Fireheart.
But the author tries to juggle four clans, each with over twenty
members, and that takes some doing!

It is fewer then say 80, but when you have more characters in Harry Potter (decent example right?) that come and go with their scenes I do think it is possible to pull it off very well. Just cannot think of anything right now on how to go about writing the endings. Since I already have their life, journey and trials written out, and most of the deaths completed, it is pulling all the strings together that gets me.

Since I built a world for this, I have already good placement of clans, politics, religion and economic issues. Even down to the types of art which are favored, and table manners. Details concern me, but it is the flow itself which causes me to stubble.