What do these people do? What does the ten years of this LP represent? Is it just for Hammer Lords that get a bit lost? Is there a reason their traits are all horrible?
They’re lords of Void Worlds, I always assumed. They have character traits, so those mean what you say they mean. I can easily imagine a Bitter and Righteous lord who’s bitter at the abandonment of his hopes, but has come out of that utterly committed to the welfare of his people and unshakable in that path. They don’t get the Forged trait because they aren’t Forged Lords, so if what you mean is “why are their traits so much less good than their seeming counterparts,” it’s because they exist in a different context. And look at those wises! This is a man who has sought and found a wisdom forbidden even to the great peerages of the Iron Empires!
Also, you could take Forged Lord as well, and the LP requires either Hammer Lord or Anvil Lord, so you’ll have at least half of the Forged trait and there are two ways to get both halves.
Ah, I thought of them as people who have gone OUT into the Void, rather than those who might have come IN from the Void as refugees, etc.
What would one use for someone who is interested in exploration? Or is Bitterness the inexorable end for all who espouse such ideas?
And surely they should have some Resources? Or at least the option to have acquired something neat from their journeys beyond the pale…
Devin’s got it. They are lords of worlds in the Void. Surrounded. Isolated. Sitting ducks. Yet defiant.
Trith’s second interpretation is fine, too! You could totally have a Void Hammer Lord who’s taken his fleet into the Void in search of lost treasure.
Is it assumed they don’t find any - and just have awful (yet illuminating) experiences - and then just go home?
It’s assumed that they’ve done it. Did they come back with goods? Are they still out there? Maybe this is a void world, and they just got here to look. Maybe yeah, he came back with the goods. A lot of that depends on your world and your concept.
Maybe you take Your Grace with trait points, make it to Hammer Lord, take Void Lord, come back with fabulous treasure and terrible weapons, and make yourself Forged Lord, king by your own hand.
Sounds good!
I think that there is an implication that something more or less ideal happens though, given that Void Lords are all Bitter.
Explaining exactly what is just the kind of thing that begs for colour, IMO. 
Did you ever read some books David Drake wrote about sort of a fictionalized space-Francis Drake? (It’s hella better than it sounds) Dude comes back from that with more loots than his society is really capable of assimilating at that time, but he’s not really anyone he would want to be, if he still had that sort of desire. But he doesn’t, now, so it’s okay. I guess.
Another way to look at it is that Void Lords are lords in the void. Why’s that? Is it because they wanted to be lords of a settled, cultured, safe world in the core and somehow ended up here instead? That sounds bitter. Is it because they won’t bend the knee and this is the only way to rule free, all dieu et mon droit and shit? Bitter!