Overall I'd say it was a genuinely fun experience if a bit on the short end; about three months long of routine sessions. The summary takes place on an Island disconnected from time and space that was conceived as an experiment between twelve or so of the greatest arcane, spiritual, and what-have-you minds from various centuries. Having willingly ascended themselves into a sort of bodiless immortality ( with which they can still interact with the physical world through masked constructs that carry some of their powers ); the experiment went wrong when one of their own betrayed them and threatened to destabilize the entire space, but it was sort of kept functioning only through the willing sacrifice of another. This sacrifice being the sibling of the one who was more or less head honcho'd the entire operation. Obviously it kind of set the tone for his attitude to anybody else trying to 'help' and making things worse, in addition to the grief of losing his family. Which is where our group comes in.
The party's reason for being there as much as any other non-immortal's was that the fluxing nature of this space created a kind of Bermuda Triangle-like effect, where shipwrecked survivors from past AND future were pulled towards it without rhyme or reason. Kind of an excuse for us to mold different types of characters as we pleased, but nobody in the group went crazy with it.
( The most was our Kobold Artificer using a bigass thunder cannon and ending up there with his tiny airship crew )
So what followed was an adventure among the other NPC survivors to try and survive and figure a way out of this place. Partly because the beings who lorded over it were different shades between:
Helpful but unwilling to go too out of the way ( Don't piss them off if you can help it, I'm sorry )
Carelessly bureaucratic about the whole mess ( Don't meddle with things beyond your understanding or we shall imprison you and release you when we have this problem sorted out ourselves. No, we are not concerned as to whether or not you end up dying of old age before that can be accomplished but your sacrifice will be noted )
Or outright hostile, which meant many of our tougher encounters consisted of PC class masked men who had different class-specific abilities tied to how they would operate and support each other in a fight, prioritizing us working together to counter.
In addition, the DM spiced things up by factoring in what he called the Fiend. Basically the BBEG who - at the start of every session - have a roll to himself via the DM to determine who among the party or NPCs slated for encounter in the story progression that session would have a chance to be doppelgangered by him. The copy wouldn't know it was one and the player had control over their character until they'd be activated and the big bad would puppet them for his purposes in an attempt to slow them down or kill them. As the story progressed, we did discover several methods and items for 'testing' ourselves or others; certain items or spells would inflict massive Radiant damage and kill the copy, salt that could be spread around our base camp to ward a puppet from entering willingly, etc. When the doppelganger was banished, usually the real character would promptly wash up on shore without memory of the period in which they had been replaced.
It had some hiccups of course, but nothing that broke the game or ever made it an unfun experience either. Mostly the DM did sense things were moving quicker towards an ending as we unwittingly discovered factors that circumvented the need to visit certain locations on the islands, so he'd loaded us up with some pretty hefty magical gear to keep us strong enough to deal with the more difficult threats while he figured things out. All in all though, the story had a pretty damn heartfelt ending as we struggled and beat the BBEG in spite of his legendary actions and quite a bit of attention paid to keep us on our toes ( like immunity to lesser spells unless engaged in a certain action, having a teleport Legendary Action, etc ) and working together. We won, we set things right and left the island to a stable timeline where our group sailed off into the distance together.
Displaced from our own times - maybe forever - but with the knowledge that we had each other, a busted airship that at least could sail the seas, and future adventures to look forward to.
So yeah, it was pretty homo but I kind of teared up when it was over. TLDR, D&D Lost was my first and - so far - best tabletop experience I've had to date. Can't wait to get into another.