For me, Thread means continuation, a one theme (possibly of many) running through something greater.
In my solo gaming, I find a recurring thread is that of treachery. Where parties of adventurers may go off to save the world, I find dealing with personal challenges and conflicts more satisfying.
My solo Zweihander [Solo rules here] solo game, dealth with Mariut, my character, being made the scapegoat for an entire crew marooned in St. Petersburg. The crew were all intending to find work in the Russian navy, where they would act as sleeper agents. Mariut, not part of the conspiracy, was made the scapegoat and blamed for the sabotage that blocked the mouth of the harbour by scuttling their ship and marooned the crew in the port. By the time the shipwreck had been dismantled sufficiently for trade to enter the port, the crew had dispersed amongst the out of work sailors.
As Mariut tried to find work, he was betrayed by the first person he turned to just to help him find his way across the city. That didn’t end well for the thug that tried to relieve Mariut of his last few coins.
He first paying job was acting as a go between for an unfaithful wife, her maid and her lover.
This particular game, I wanted it to be low magic, verging on no magic. If you are bleeding out in a gutter, you are very likely to die. There is a suggestion of dark forces. In this case it is a Rasputin-esque monk supposedly exerting unnatural influence of the ladies of the Tzar’s court.
It is entirely possible that one day that Mariut will come face to face with this monk and in a position to confront him. But that is not an adventure for today.
The continuity is provided by this thread of treachery and betrayal. It fits into the grim and perilous world of Zweihander, possibly better than it would a world cast in terms of D20 combat. In D20 terms, your character would never be in dire need of a surgeon, if you lost most of your hit points you just sleep it off. Zweihander is not like that!
In d20-land combat is almost sought out. In Zweihander it is best avoided. If you cannot avoid it, then you fight like your life depend on it.
I would not really describe my Zweihander game as a campaign. As I wrote on Sunday, I have barely explored more than half a dozen streets in a rough triangle. What brings it all together is today’s prompt, that thematic thread of betrayal, both personal and political.